gn build: Pass -fno-sanitize=vptr,function with use_ubsan

Matches CMake LLVM_UBSAN_FLAGS.

Reviewers: aeubanks

Reviewed By: aeubanks

Pull Request: llvm#93911

llvm/utils/gn/build/BUILD.gn

@@ -375,6 +375,7 @@ config("compiler_defaults") {
  "ubsan only supported on iOS/Clang, Linux/Clang, or macOS/Clang")
  cflags += [
  "-fsanitize=undefined",
+ "-fno-sanitize=vptr,function",
  "-fno-sanitize-recover=all",
  ]
  ldflags += [ "-fsanitize=undefined" ]