GN: support 32-bit x86 builds

infra/bots/recipes/swarm_compile.expected/failed_compile.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport sys, os\npath = sys.argv[1]\nmode = int(sys.argv[2])\nif not os.path.isdir(path):\n  if os.path.exists(path):\n    print \"%s exists but is not a dir\" % path\n    sys.exit(1)\n  os.makedirs(path, mode)\n",
       "[CUSTOM_/_B_WORK]",
       "511"
     ],
     "name": "makedirs checkout_path",
@@ skipping 17 matching lines @@
       "RECIPE_PACKAGE_REPO[depot_tools]/gclient.py",
       "config",
       "--spec",
       "cache_dir = '[CUSTOM_/_B_CACHE]'\nsolutions = [{'deps_file': '.DEPS.git', 'managed': False, 'name': 'skia', 'url': 'https://skia.googlesource.com/skia.git'}]"
     ],
     "cwd": "[CUSTOM_/_B_WORK]",
     "env": {
       "BUILDTYPE": "Debug",
       "CHROME_HEADLESS": "1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]",
-      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86-Debug"
+      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Debug"
     },
     "name": "gclient setup"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[depot_tools]/gclient.py",
       "sync",
       "--verbose",
       "--with_branch_heads",
       "--nohooks",
       "-j8",
       "--reset",
       "--force",
       "--upstream",
       "--no-nag-max",
       "--delete_unversioned_trees",
       "--revision",
       "skia@abc123",
       "--output-json",
       "/path/to/tmp/json"
     ],
     "cwd": "[CUSTOM_/_B_WORK]",
     "env": {
       "BUILDTYPE": "Debug",
       "CHROME_HEADLESS": "1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]",
-      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86-Debug"
+      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Debug"
     },
     "name": "gclient sync",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"solutions\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"skia/\": {@@@",
       "@@@STEP_LOG_LINE@json.output@      \"revision\": \"9046e2e693bb92a76e972b694580e5d17ad10748\"@@@",
       "@@@STEP_LOG_LINE@json.output@    }@@@",
       "@@@STEP_LOG_LINE@json.output@  }@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
@@ skipping 10 matching lines @@
       "git",
       "config",
       "user.name",
       "local_bot"
     ],
     "cwd": "[CUSTOM_/_B_WORK]",
     "env": {
       "BUILDTYPE": "Debug",
       "CHROME_HEADLESS": "1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]",
-      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86-Debug"
+      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Debug"
     },
     "name": "gclient recurse (git config user.name)"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[depot_tools]/gclient.py",
       "recurse",
       "git",
       "config",
       "user.email",
       "local_bot@example.com"
     ],
     "cwd": "[CUSTOM_/_B_WORK]",
     "env": {
       "BUILDTYPE": "Debug",
       "CHROME_HEADLESS": "1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]",
-      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86-Debug"
+      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Debug"
     },
     "name": "gclient recurse (git config user.email)"
   },
   {
     "cmd": [
       "make",
       "most"
     ],
     "cwd": "[CUSTOM_/_B_WORK]/skia",
     "env": {
       "BUILDTYPE": "Debug",
       "CHROME_HEADLESS": "1",
       "CHROME_PATH": "[SLAVE_BUILD]/src",
-      "GYP_DEFINES": "skia_arch_type=x86 skia_warnings_as_errors=1",
+      "GYP_DEFINES": "skia_arch_type=x86_64 skia_warnings_as_errors=1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]:RECIPE_PACKAGE_REPO[depot_tools]",
-      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86-Debug"
+      "SKIA_OUT": "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Debug"
     },
     "name": "build most",
     "~followup_annotations": [
       "step returned non-zero exit code: 1",
       "@@@STEP_FAILURE@@@"
     ]
   },
   {
     "name": "$result",
     "reason": "Step('build most') failed with return_code 1",
     "recipe_result": null,
     "status_code": 1
   }
 ]