libyuv: Add Android x86, x64 and MIPS bots.

scripts/slave/recipes/libyuv/libyuv.expected/tryserver_libyuv_android_mips.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "tryserver.libyuv",
       "--builder",
-      "android_clang",
+      "android_mips",
       "--slave",
       "slavename",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'custom_vars': {'root_dir': 'src'}, 'deps_file': 'DEPS', 'managed': True, 'name': 'src', 'url': 'https://chromium.googlesource.com/libyuv/libyuv'}]\ntarget_os = ['android']",
       "--root",
       "src",
       "--revision_mapping_file",
       "{}",
       "--git-cache-dir",
       "[GIT_CACHE]",
@@ skipping 31 matching lines @@
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[depot_tools]/gclient.py",
       "runhooks"
     ],
     "cwd": "[SLAVE_BUILD]/src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "GYP_CROSSCOMPILE": "1",
-      "GYP_DEFINES": "OS=android clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' target_arch=arm use_goma=1",
+      "GYP_DEFINES": "OS=android clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[BUILD]/goma' target_arch=mipsel use_goma=1",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "gclient runhooks"
   },
   {
     "allow_subannotations": true,
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/clang_revision.py",
@@ skipping 55 matching lines @@
       "@@@STEP_LOG_LINE@json.output (invalid)@null@@@",
       "@@@STEP_LOG_END@json.output (invalid)@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]