diff --git a/libcxx/test/configs/apple-libc++-shared.cfg.in b/libcxx/test/configs/apple-libc++-shared.cfg.in
--- a/libcxx/test/configs/apple-libc++-shared.cfg.in
+++ b/libcxx/test/configs/apple-libc++-shared.cfg.in
@@ -7,21 +7,19 @@
 # We also don't use a per-target include directory layout, so we have only one
 # include directory for the libc++ headers.
 
-import sys
-
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}',
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{install}/include/c++/v1 -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '%{user_compile_flags} -nostdinc++ -isystem %{install}/include/c++/v1 -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib++ -L %{install}/lib -lc++'
+    '%{user_link_flags} -nostdlib++ -L %{install}/lib -lc++'
 ))
 config.substitutions.append(('%{exec}',
-    '{} %{{libcxx}}/utils/run.py --execdir %T --env DYLD_LIBRARY_PATH=%{{install}}/lib -- '.format(sys.executable)
+    '%{executor} --execdir %T --env DYLD_LIBRARY_PATH=%{install}/lib -- '
 ))
 
 import os, site
diff --git a/libcxx/test/configs/cmake-bridge.cfg.in b/libcxx/test/configs/cmake-bridge.cfg.in
--- a/libcxx/test/configs/cmake-bridge.cfg.in
+++ b/libcxx/test/configs/cmake-bridge.cfg.in
@@ -29,3 +29,6 @@
 config.substitutions.append(('%{include}', '%{install}/@LIBCXX_INSTALL_INCLUDE_DIR@'))
 config.substitutions.append(('%{target-include}', '%{install}/@LIBCXX_INSTALL_INCLUDE_TARGET_DIR@'))
 config.substitutions.append(('%{lib}', '%{install}/@LIBCXX_INSTALL_LIBRARY_DIR@'))
+config.substitutions.append(('%{executor}', '@LIBCXX_EXECUTOR@'))
+config.substitutions.append(('%{user_compile_flags}', '@LIBCXX_TEST_COMPILER_FLAGS@'))
+config.substitutions.append(('%{user_link_flags}', '@LIBCXX_TEST_LINKER_FLAGS@'))
diff --git a/libcxx/test/configs/ibm-libc++-shared.cfg.in b/libcxx/test/configs/ibm-libc++-shared.cfg.in
--- a/libcxx/test/configs/ibm-libc++-shared.cfg.in
+++ b/libcxx/test/configs/ibm-libc++-shared.cfg.in
@@ -2,19 +2,17 @@
 # AIX using a shared library.
 #
 
-import sys
-
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}', ''))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -D__LIBC_NO_CPP_MATH_OVERLOADS__ -isystem %{install}/include/c++/v1 -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '%{user_compile_flags} -nostdinc++ -D__LIBC_NO_CPP_MATH_OVERLOADS__ -isystem %{install}/include/c++/v1 -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib++ -L %{install}/lib -lc++ -lc++abi -latomic -Wl,-bbigtoc'
+    '%{user_link_flags} -nostdlib++ -L %{install}/lib -lc++ -lc++abi -latomic -Wl,-bbigtoc'
 ))
 config.substitutions.append(('%{exec}',
-    '{} %{{libcxx}}/utils/run.py --execdir %T --env LIBPATH=%{{install}}/lib -- '.format(sys.executable)
+    '%{executor} --execdir %T --env LIBPATH=%{install}/lib -- '
 ))
 
 # LIBCXX-AIX-FIXME is the feature name used to XFAIL the
diff --git a/libcxx/test/configs/llvm-libc++-shared-gcc.cfg.in b/libcxx/test/configs/llvm-libc++-shared-gcc.cfg.in
--- a/libcxx/test/configs/llvm-libc++-shared-gcc.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-shared-gcc.cfg.in
@@ -2,19 +2,17 @@
 # using a shared library, with GCC. This is done differently from Clang because
 # GCC does not support the -nostdlib++ command-line flag.
 
-import sys
-
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}', ''))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '%{user_compile_flags} -nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
 ))
 config.substitutions.append(('%{link_flags}',
-    '-L %{lib} -Wl,-rpath,%{lib} -nodefaultlibs -lc++ -lm -lgcc_s -lgcc -lpthread -lc -lgcc_s -lgcc -latomic'
+    '%{user_link_flags} -L %{lib} -Wl,-rpath,%{lib} -nodefaultlibs -lc++ -lm -lgcc_s -lgcc -lpthread -lc -lgcc_s -lgcc -latomic'
 ))
 config.substitutions.append(('%{exec}',
-    '{} %{{libcxx}}/utils/run.py --execdir %T -- '.format(sys.executable)
+    '%{executor} --execdir %T -- '
 ))
 
 import os, site
diff --git a/libcxx/test/configs/llvm-libc++-shared.cfg.in b/libcxx/test/configs/llvm-libc++-shared.cfg.in
--- a/libcxx/test/configs/llvm-libc++-shared.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-shared.cfg.in
@@ -1,21 +1,19 @@
 # This testing configuration handles running the test suite against LLVM's libc++
 # using a shared library.
 
-import sys
-
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}',
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '%{user_compile_flags} -nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -pthread'
+    '%{user_link_flags} -nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -pthread'
 ))
 config.substitutions.append(('%{exec}',
-    '{} %{{libcxx}}/utils/run.py --execdir %T -- '.format(sys.executable)
+    '%{executor} --execdir %T -- '
 ))
 
 import os, site
diff --git a/libcxx/test/configs/llvm-libc++-static.cfg.in b/libcxx/test/configs/llvm-libc++-static.cfg.in
--- a/libcxx/test/configs/llvm-libc++-static.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-static.cfg.in
@@ -1,21 +1,19 @@
 # This testing configuration handles running the test suite against LLVM's libc++
 # using a static library.
 
-import sys
-
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}',
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '%{user_compile_flags} -nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
 ))
 config.substitutions.append(('%{link_flags}',
-    '-nostdlib++ -L %{lib} -lc++ -lc++abi -pthread'
+    '%{user_link_flags} -nostdlib++ -L %{lib} -lc++ -lc++abi -pthread'
 ))
 config.substitutions.append(('%{exec}',
-    '{} %{{libcxx}}/utils/run.py --execdir %T -- '.format(sys.executable)
+    '%{executor} --execdir %T -- '
 ))
 
 import os, site
diff --git a/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in b/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in
--- a/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in
+++ b/libcxxabi/test/configs/apple-libc++abi-shared.cfg.in
@@ -1,7 +1,5 @@
 # Testing configuration for Apple's system libc++abi.
 
-import sys
-
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}',
@@ -15,7 +13,7 @@
     '-nostdlib++ -L %{install}/lib -lc++ -lc++abi'
 ))
 config.substitutions.append(('%{exec}',
-    '{} %{{libcxx}}/utils/run.py --execdir %T --env DYLD_LIBRARY_PATH=%{{install}}/lib -- '.format(sys.executable)
+    '%{executor} --execdir %T --env DYLD_LIBRARY_PATH=%{install}/lib -- '
 ))
 
 import os, site
diff --git a/libcxxabi/test/configs/cmake-bridge.cfg.in b/libcxxabi/test/configs/cmake-bridge.cfg.in
--- a/libcxxabi/test/configs/cmake-bridge.cfg.in
+++ b/libcxxabi/test/configs/cmake-bridge.cfg.in
@@ -29,3 +29,4 @@
 config.substitutions.append(('%{cxx}', '@CMAKE_CXX_COMPILER@'))
 config.substitutions.append(('%{libcxx}', '@LIBCXXABI_LIBCXX_PATH@'))
 config.substitutions.append(('%{install}', '@CMAKE_BINARY_DIR@'))
+config.substitutions.append(('%{executor}', '@LIBCXXABI_EXECUTOR@'))
diff --git a/libcxxabi/test/configs/ibm-libc++abi-shared.cfg.in b/libcxxabi/test/configs/ibm-libc++abi-shared.cfg.in
--- a/libcxxabi/test/configs/ibm-libc++abi-shared.cfg.in
+++ b/libcxxabi/test/configs/ibm-libc++abi-shared.cfg.in
@@ -1,7 +1,5 @@
 # Testing configuration for libc++abi on AIX.
 
-import sys
-
 lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
 
 config.substitutions.append(('%{flags}',''))
@@ -15,7 +13,7 @@
     '-nostdlib++ -L %{install}/lib -lc++ -lc++abi -Wl,-bbigtoc'
 ))
 config.substitutions.append(('%{exec}',
-    '{} %{{libcxx}}/utils/run.py --execdir %T --env LIBPATH=%{{install}}/lib -- '.format(sys.executable)
+    '%{executor} --execdir %T --env LIBPATH=%{install}/lib -- '
 ))
 
 import os, site