android: Add a way to override build system variables.

test/android/settings.gyp

Index: test/android/settings.gyp
diff --git a/test/android/hello.gyp b/test/android/settings.gyp
similarity index 78%
copy from test/android/hello.gyp
copy to test/android/settings.gyp
index da58a2b707f8f15d4402ff4889fef052800c55f4..d89eee2db2760c878c7355578f4b573ef3214f7c 100644
--- a/test/android/hello.gyp
+++ b/test/android/settings.gyp
@@ -10,6 +10,9 @@
       'sources': [
         'hello.c',
       ],
+      'android_build_settings': {
+        'LOCAL_MODULE_SUFFIX': '.foo',
+      }
     },
   ],
 }