[gn build] (manually) port b4a99a0

Author: nico

llvm/utils/gn/secondary/clang/include/clang/Config/BUILD.gn

@@ -28,6 +28,7 @@ write_cmake_config("Config") {
     "C_INCLUDE_DIRS=",
     "CLANG_CONFIG_FILE_SYSTEM_DIR=",
     "CLANG_CONFIG_FILE_USER_DIR=",
+    "CLANG_SPAWN_CC1=0",
     "DEFAULT_SYSROOT=",
     "GCC_INSTALL_PREFIX=",
     "BACKEND_PACKAGE_STRING=LLVM ${llvm_version}git",