Various GN fixes.

- Fixes gcc_version issues on gTrusty.
- Fixes accidental duplicate in input_events build file.
- Fixes spammy warnings in libxml.

BUG=none
TEST=builds

Review URL: https://codereview.chromium.org/518543004

Cr-Commit-Position: refs/heads/master@{#292669}

build/config/gcc/gcc_version.gni

@@ -2,7 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-if (is_android) {
+if (is_clang) {
+  gcc_version = 0
+} else if (is_android) {
   gcc_version = 48
 } else {
   gcc_version = exec_script("../../compiler_version.py", [ "host",  "compiler" ], "value")

mojo/services/public/cpp/input_events/BUILD.gn

@@ -22,7 +22,7 @@ component("input_events") {
 
   sources = [
     "lib/input_events_type_converters.cc",
-    "lib/input_events_type_converters.cc",
+    "lib/input_events_type_converters.h",
     "lib/mojo_extended_key_event_data.cc",
     "lib/mojo_extended_key_event_data.h",
     "input_events_type_converters.h",

third_party/libxml/BUILD.gn

@@ -174,6 +174,10 @@ static_library("libxml") {
 
       # debugXML.c compares array 'arg' to NULL.
       "-Wno-tautological-pointer-compare",
+
+      # threads.c attempts to forward declare a pthread_equal which doesn't
+      # match the prototype in pthreads.h
+      "-Wno-ignored-attributes",
     ]
   }