allow_posix_link_time_opt and is_cfi are clang features

build/toolchain/toolchain.gni

Index: build/toolchain/toolchain.gni
diff --git a/build/toolchain/toolchain.gni b/build/toolchain/toolchain.gni
index 6eb3c9080393b1b80c79650257bcdd0b5dd745d9..922a9c7d39933114fb9da51f298dd3cd60f2e7c9 100644
--- a/build/toolchain/toolchain.gni
+++ b/build/toolchain/toolchain.gni
@@ -13,8 +13,9 @@ declare_args() {
   # faster, but linking is up to 5-20x slower).
   # Note: use target_os == "linux" rather than is_linux so that it does not
   # apply to host_toolchain when target_os="android".
-  allow_posix_link_time_opt = target_os == "linux" && !is_chromeos &&
-                              target_cpu == "x64" && is_official_build
+  allow_posix_link_time_opt =
+      is_clang && target_os == "linux" && !is_chromeos && target_cpu == "x64" &&
+      is_official_build
 
   # Set to true to use lld, the LLVM linker. This flag may be used on Windows
   # with the shipped LLVM toolchain, or on Linux with a self-built top-of-tree