Really suppress -Wswitch warnings in third_party/yasm for GN build.

third_party/yasm/BUILD.gn

 # Copyright 2014 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.
 
 # The yasm build process creates a slew of small C subprograms that
 # dynamically generate files at various point in the build process.  This makes
 # the build integration moderately complex.
 #
 # There are three classes of dynamically generated files:
 #   1) C source files that should be included in the build (eg., lc3bid.c)
@@ skipping 130 matching lines @@
       "source/patched-yasm/tools/re2c/code.c",
       "source/patched-yasm/tools/re2c/dfa.c",
       "source/patched-yasm/tools/re2c/main.c",
       "source/patched-yasm/tools/re2c/mbo_getopt.c",
       "source/patched-yasm/tools/re2c/parser.c",
       "source/patched-yasm/tools/re2c/scanner.c",
       "source/patched-yasm/tools/re2c/substr.c",
       "source/patched-yasm/tools/re2c/translate.c",
     ]
 
+    config("re2c_warnings") {
+      # re2c is missing CLOSEVOP from one switch.
+      if (is_posix || is_clang) {
+        cflags = [ "-Wno-switch" ]
+      }
+    }
+
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [
       ":yasm_config",
       "//build/config/compiler:no_chromium_code",
+      ":re2c_warnings",
     ]
-
-    # re2c is missing CLOSEVOP from one switch.
-    if (is_posix) {
-      cflags = [ "-Wno-switch" ]
-    }
     deps = [
       "//build/config/sanitizers:deps",
     ]
   }
 
   executable("yasm") {
     sources = [
       "source/patched-yasm/frontends/yasm/yasm-options.c",
       "source/patched-yasm/frontends/yasm/yasm.c",
       "source/patched-yasm/libyasm/assocdat.c",
@@ skipping 317 matching lines @@
 
     # Output eventually #included by source/patched-yasm/frontends/yasm/x86id.c
     outputs = [
       "$yasm_gen_include_dir/x86insns.c",
       "$yasm_gen_include_dir/x86insn_gas.gperf",
       "$yasm_gen_include_dir/x86insn_nasm.gperf",
     ]
     args = [ rebase_path(yasm_gen_include_dir, root_build_dir) ]
   }
 }