diff --git a/libcxx/test/CMakeLists.txt b/libcxx/test/CMakeLists.txt
--- a/libcxx/test/CMakeLists.txt
+++ b/libcxx/test/CMakeLists.txt
@@ -26,6 +26,11 @@
   serialize_lit_param(enable_assertions True)
 endif()
 
+if (NOT LIBCXX_TEST_COMPILER)
+  set(LIBCXX_TEST_COMPILER "${CMAKE_CXX_COMPILER}" CACHE PATH
+    "Path to the Lit test compiler.")
+endif()
+
 if (CMAKE_CXX_COMPILER_TARGET)
   serialize_lit_param(target_triple "\"${CMAKE_CXX_COMPILER_TARGET}\"")
 else()
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
@@ -24,7 +24,7 @@
 
 # Add substitutions for bootstrapping the test suite configuration
 import shlex
-config.substitutions.append(('%{cxx}', shlex.quote('@CMAKE_CXX_COMPILER@')))
+config.substitutions.append(('%{cxx}', shlex.quote('@LIBCXX_TEST_COMPILER@')))
 config.substitutions.append(('%{libcxx}', '@LIBCXX_SOURCE_DIR@'))
 config.substitutions.append(('%{include}', '@LIBCXX_GENERATED_INCLUDE_DIR@'))
 config.substitutions.append(('%{target-include}', '@LIBCXX_GENERATED_INCLUDE_TARGET_DIR@'))
diff --git a/libcxxabi/test/CMakeLists.txt b/libcxxabi/test/CMakeLists.txt
--- a/libcxxabi/test/CMakeLists.txt
+++ b/libcxxabi/test/CMakeLists.txt
@@ -47,6 +47,11 @@
   serialize_lit_param(use_sanitizer "\"${LLVM_USE_SANITIZER}\"")
 endif()
 
+if (NOT LIBCXX_TEST_COMPILER)
+  set(LIBCXX_TEST_COMPILER "${CMAKE_CXX_COMPILER}" CACHE PATH
+    "Path to the Lit test compiler.")
+endif()
+
 if (CMAKE_CXX_COMPILER_TARGET)
   serialize_lit_param(target_triple "\"${CMAKE_CXX_COMPILER_TARGET}\"")
 else()
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
@@ -26,7 +26,7 @@
 # TODO: This is a non-standard Lit attribute and we should have another way of accessing this.
 config.host_triple = '@LLVM_HOST_TRIPLE@'
 
-config.substitutions.append(('%{cxx}', '@CMAKE_CXX_COMPILER@'))
+config.substitutions.append(('%{cxx}', '@LIBCXX_TEST_COMPILER@'))
 config.substitutions.append(('%{libcxx}', '@LIBCXXABI_LIBCXX_PATH@'))
 config.substitutions.append(('%{include}', '@LIBCXXABI_SOURCE_DIR@/include'))
 config.substitutions.append(('%{cxx-include}', '@LIBCXXABI_HEADER_DIR@/include/c++/v1'))
diff --git a/libunwind/test/CMakeLists.txt b/libunwind/test/CMakeLists.txt
--- a/libunwind/test/CMakeLists.txt
+++ b/libunwind/test/CMakeLists.txt
@@ -26,6 +26,11 @@
   serialize_lit_param(use_sanitizer "\"${LLVM_USE_SANITIZER}\"")
 endif()
 
+if (NOT LIBCXX_TEST_COMPILER)
+  set(LIBCXX_TEST_COMPILER "${CMAKE_CXX_COMPILER}" CACHE PATH
+    "Path to the Lit test compiler.")
+endif()
+
 if (CMAKE_CXX_COMPILER_TARGET)
   serialize_lit_param(target_triple "\"${CMAKE_CXX_COMPILER_TARGET}\"")
 else()
diff --git a/libunwind/test/configs/cmake-bridge.cfg.in b/libunwind/test/configs/cmake-bridge.cfg.in
--- a/libunwind/test/configs/cmake-bridge.cfg.in
+++ b/libunwind/test/configs/cmake-bridge.cfg.in
@@ -30,7 +30,7 @@
 
 # Add substitutions for bootstrapping the test suite configuration
 import shlex
-config.substitutions.append(('%{cxx}', shlex.quote('@CMAKE_CXX_COMPILER@')))
+config.substitutions.append(('%{cxx}', shlex.quote('@LIBCXX_TEST_COMPILER@')))
 config.substitutions.append(('%{executor}', '@LIBUNWIND_EXECUTOR@'))
 config.substitutions.append(('%{include}', '@LIBUNWIND_SOURCE_DIR@/include'))
 config.substitutions.append(('%{lib}', '@LIBUNWIND_LIBRARY_DIR@'))