Index: libcxx/test/lit.site.cfg.in
===================================================================
--- libcxx/test/lit.site.cfg.in
+++ libcxx/test/lit.site.cfg.in
@@ -28,6 +28,7 @@
 config.executor                 = "@LIBCXX_EXECUTOR@"
 config.llvm_unwinder            = "@LIBCXXABI_USE_LLVM_UNWINDER@"
 config.compiler_rt              = "@LIBCXX_USE_COMPILER_RT@"
+config.builtins_library         = "@LIBCXX_BUILTINS_LIBRARY@"
 config.has_libatomic            = "@LIBCXX_HAS_ATOMIC_LIB@"
 config.use_libatomic            = "@LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB@"
 config.debug_build              = "@LIBCXX_DEBUG_BUILD@"
Index: libcxx/utils/libcxx/test/target_info.py
===================================================================
--- libcxx/utils/libcxx/test/target_info.py
+++ libcxx/utils/libcxx/test/target_info.py
@@ -252,7 +252,11 @@
         else:
             flags += ['-lgcc_s']
         compiler_rt = self.full_config.get_lit_bool('compiler_rt', False)
-        if not compiler_rt:
+        if compiler_rt:
+            builtins_lib = self.full_config.get_lit_conf('builtins_library')
+            if builtins_lib:
+                flags += [builtins_lib]
+        else:
             flags += ['-lgcc']
         use_libatomic = self.full_config.get_lit_bool('use_libatomic', False)
         if use_libatomic:
Index: libcxxabi/test/lit.site.cfg.in
===================================================================
--- libcxxabi/test/lit.site.cfg.in
+++ libcxxabi/test/lit.site.cfg.in
@@ -9,6 +9,7 @@
 config.libunwind_headers        = "@LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL@"
 config.cxx_library_root         = "@LIBCXXABI_LIBCXX_LIBRARY_PATH@"
 config.llvm_unwinder            = "@LIBCXXABI_USE_LLVM_UNWINDER@"
+config.builtins_library         = "@LIBCXXABI_BUILTINS_LIBRARY@"
 config.enable_threads           = "@LIBCXXABI_ENABLE_THREADS@"
 config.use_sanitizer            = "@LLVM_USE_SANITIZER@"
 config.sanitizer_library        = "@LIBCXXABI_SANITIZER_LIBRARY@"
Index: libunwind/test/lit.site.cfg.in
===================================================================
--- libunwind/test/lit.site.cfg.in
+++ libunwind/test/lit.site.cfg.in
@@ -8,6 +8,7 @@
 config.libunwind_headers        = "@LIBUNWIND_SOURCE_DIR@/include"
 config.cxx_library_root         = "@LIBUNWIND_LIBCXX_LIBRARY_PATH@"
 config.llvm_unwinder            = "1"
+config.builtins_library         = "@LIBUNWIND_BUILTINS_LIBRARY@"
 config.enable_threads           = "@LIBUNWIND_ENABLE_THREADS@"
 config.use_sanitizer            = "@LLVM_USE_SANITIZER@"
 config.enable_32bit             = "@LIBUNWIND_BUILD_32_BITS@"