[libc++] Fix linking benchmarks (llvm#116495)

On my system the library path ends with `lib64` instead of `lib`.

Author: philnik777

libcxx/test/configs/cmake-bridge.cfg.in

@@ -30,4 +30,4 @@ config.substitutions.append(('%{target-include-dir}', '@LIBCXX_TESTING_INSTALL_P
 config.substitutions.append(('%{lib-dir}', '@LIBCXX_TESTING_INSTALL_PREFIX@/@LIBCXX_INSTALL_LIBRARY_DIR@'))
 config.substitutions.append(('%{module-dir}', '@LIBCXX_TESTING_INSTALL_PREFIX@/@LIBCXX_INSTALL_MODULES_DIR@'))
 config.substitutions.append(('%{test-tools-dir}', '@LIBCXX_TEST_TOOLS_PATH@'))
-config.substitutions.append(('%{benchmark_flags}', '-I @LIBCXX_BINARY_DIR@/test/benchmarks/google-benchmark/include -L @LIBCXX_BINARY_DIR@/test/benchmarks/google-benchmark/lib -l benchmark'))
+config.substitutions.append(('%{benchmark_flags}', '-I @LIBCXX_BINARY_DIR@/test/benchmarks/google-benchmark/include -L @LIBCXX_BINARY_DIR@/test/benchmarks/google-benchmark/lib -L @LIBCXX_BINARY_DIR@/test/benchmarks/google-benchmark/lib64 -l benchmark'))