[gn build] (manually) merge 5eedf07

Author: nico

llvm/utils/gn/secondary/clang/test/BUILD.gn

@@ -48,6 +48,7 @@ write_lit_config("lit_site_cfg") {
     "CLANG_DEFAULT_CXX_STDLIB=",  # Empty string means "default value" here.
     "CLANG_DEFAULT_LINKER=",
     "CLANG_TOOLS_DIR=" + rebase_path("$root_out_dir/bin", dir),
+    "CLANG_VENDOR_UTI=org.llvm.clang",
 
     # This is only used if LLVM_USE_SANITIZER includes lsan and the host
     # OS is macOS. Since the GN build currently never uses LLVM_USE_SANITIZER,