win: /PROFILE works fine with clang.

build/config/win/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/clang/clang.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 68 matching lines @@
 
     # Clang runtime libraries, such as the sanitizer runtimes, live here.
     lib_dirs = [ "$clang_base_path/lib/clang/$clang_version/lib/windows" ]
   }
 
   # /PROFILE ensures that the PDB file contains FIXUP information (growing the
   # PDB file by about 5%) but does not otherwise alter the output binary. This
   # information is used by the Syzygy optimization tool when decomposing the
   # release image. It is enabled for syzyasan builds and opportunistically for
   # other builds where it is not prohibited (not supported when incrementally
-  # linking, using /debug:fastlink, or building with clang).
+  # linking, or using /debug:fastlink).
   if (is_syzyasan) {
     assert(!is_win_fastlink)
     ldflags = [ "/PROFILE" ]
   } else {
     if (!is_debug && !is_component_build) {
-      if (is_win_fastlink || is_clang) {
+      if (is_win_fastlink) {
         # /PROFILE implies the following linker flags. Therefore if we are
         # skipping /PROFILE because it is incompatible with /DEBUG:FASTLINK
         # we should explicitly add these flags in order to avoid unintended
         # consequences such as larger binaries.
         ldflags = [
           "/OPT:REF",
           "/OPT:ICF",
           "/INCREMENTAL:NO",
           "/FIXED:NO",
         ]
@@ skipping 309 matching lines @@
 
 # Internal stuff --------------------------------------------------------------
 
 # Config used by the MIDL template to disable warnings.
 config("midl_warnings") {
   if (is_clang) {
     # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_".
     cflags = [ "-Wno-extra-tokens" ]
   }
 }