Prepare for -Wall for third-party code, -Wextra for chromium_code

third_party/mach_override/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.
 
+config("libudis86_warnings") {
+  if (is_clang) {
+    cflags = [
+      # syn.c contains a switch with an assert(false) in a default:
+      # block.  In release builds, the function is missing a return.
+      "-Wno-return-type",
+
+      # Fires once in decode.c.
+      "-Wno-sometimes-uninitialized",
+    ]
+  }
+}
+
 static_library("libudis86") {
   sources = [
     "libudis86/decode.c",
     "libudis86/decode.h",
     "libudis86/extern.h",
     "libudis86/input.c",
     "libudis86/input.h",
     "libudis86/itab.c",
     "libudis86/itab.h",
     "libudis86/syn-att.c",
     "libudis86/syn-intel.c",
     "libudis86/syn.c",
     "libudis86/syn.h",
     "libudis86/types.h",
     "libudis86/udint.h",
     "libudis86/udis86.c",
     "udis86.h",
   ]
   defines = [
     "HAVE_ASSERT_H",
     "HAVE_STRING_H",
   ]
 
   # syn.c doesn't specify a return value when it issues an assertion.
   cflags = [ "-Wno-return-type" ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
+  configs += [
+    "//build/config/compiler:no_chromium_code",
+
+    # Must be after no_chromium_code for warning flags to be ordered correctly.
+    ":libudis86_warnings",
+  ]
 
   if (is_clang) {
     # For UD_ASSERT(!"message");
     configs -= [ "//build/config/clang:extra_warnings" ]
   }
 }
 
 static_library("mach_override") {
   sources = [
     "mach_override.c",
     "mach_override.h",
   ]
   deps = [
     ":libudis86",
   ]
 }