recipes/win: Stop explicitly disabling precompiled headers in recipes in goma builds.

scripts/slave/recipes/win_analyze.expected/full_chromium_fyi_Chromium_Windows_Analyze.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]\\resources\\bot_update.py",
       "--master",
       "chromium.fyi",
       "--builder",
       "Chromium Windows Analyze",
@@ skipping 116 matching lines @@
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[depot_tools]\\gclient.py",
       "runhooks"
     ],
     "cwd": "[SLAVE_BUILD]\\src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "C:\\creds\\service_accounts\\service-account-goma-client.json",
       "GYP_CHROMIUM_NO_ACTION": "1",
-      "GYP_DEFINES": "chromium_win_pch=0 component=shared_library fastbuild=2 gomadir='[BUILD]\\goma' target_arch=ia32 use_goma=0 win_analyze=1",
+      "GYP_DEFINES": "component=shared_library fastbuild=2 gomadir='[BUILD]\\goma' target_arch=ia32 use_goma=0 win_analyze=1",

[Nico, 2016/07/13 18:31:41]

This diff is a bit surprising since this passes use_goma=0 and still loses the
flag. This is because
https://cs.chromium.org/chromium/build/scripts/slave/recipes/win_analyze.py?r...
does strange things. Since the bot is on mb, this doesn't have an effect though.

       "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]\\src\\tools\\mb\\mb.py",
       "gen",
@@ skipping 35 matching lines @@
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "C:\\creds\\service_accounts\\service-account-goma-client.json"
     },
     "name": "compile"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]