Skia: Supply --gcc to android_ninja when appropriate

scripts/slave/recipes/skia/skia.expected/Test-Android-GCC-Nexus7-GPU-Tegra3-Arm7-Debug.json

 [
   {
     "cmd": [
       "git",
       "remote",
       "set-url",
       "origin",
       "https://skia.googlesource.com/skia.git"
     ],
     "cwd": "[SLAVE_BUILD]/skia",
@@ skipping 151 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  pass@@@",
       "@@@STEP_LOG_LINE@python.inline@print json.dumps({'ccache': ccache})@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "cmd": [
       "[SLAVE_BUILD]/skia/platform_tools/android/bin/android_ninja",
       "dm",
       "-d",
-      "arm_v7_neon"
+      "arm_v7_neon",
+      "--gcc"
     ],
     "cwd": "[SLAVE_BUILD]/skia",
     "env": {
       "ANDROID_HOME": "/home/chrome-bot/android-sdk-linux",
       "ANDROID_SDK_ROOT": "/home/chrome-bot/android-sdk-linux",
       "BUILDTYPE": "Debug",
       "GYP_DEFINES": "skia_arch_type=arm skia_warnings_as_errors=0",
       "SKIA_ANDROID_VERBOSE_SETUP": "1",
       "SKIA_OUT": "[SLAVE_BUILD]/skia/out/Test-Android-GCC-Nexus7-GPU-Tegra3-Arm7-Debug"
     },
     "name": "build dm"
   },
   {
     "cmd": [
       "[SLAVE_BUILD]/skia/platform_tools/android/bin/android_ninja",
       "nanobench",
       "-d",
-      "arm_v7_neon"
+      "arm_v7_neon",
+      "--gcc"
     ],
     "cwd": "[SLAVE_BUILD]/skia",
     "env": {
       "ANDROID_HOME": "/home/chrome-bot/android-sdk-linux",
       "ANDROID_SDK_ROOT": "/home/chrome-bot/android-sdk-linux",
       "BUILDTYPE": "Debug",
       "GYP_DEFINES": "skia_arch_type=arm skia_warnings_as_errors=0",
       "SKIA_ANDROID_VERBOSE_SETUP": "1",
       "SKIA_OUT": "[SLAVE_BUILD]/skia/out/Test-Android-GCC-Nexus7-GPU-Tegra3-Arm7-Debug"
     },
@@ skipping 671 matching lines @@
       "SKIA_OUT": "[SLAVE_BUILD]/skia/out/Test-Android-GCC-Nexus7-GPU-Tegra3-Arm7-Debug"
     },
     "name": "wait for charge (3)"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]