Fix --no-gles config, and ease the pain of standalone emulator build

1. Apparently, emulator build fails when configured with --no-gles option due to
   missing android_setPostCallback implementation.
2. It's painful to configure standalone emulator build WITH OpenGLES, since it requires
   explicit using of --gles-include, and --gles-lib when launching android-configure.sh
   To ease that pain, just use default location for standalone emulator build.

Change-Id: I2d9ed56d68a4ab1cb1ec294817f22dca80d33223
diff --git a/android/opengles.c b/android/opengles.c
index b265428..f56252c 100644
--- a/android/opengles.c
+++ b/android/opengles.c
@@ -283,6 +283,11 @@
     return -1;
 }
 
+void
+android_setPostCallback(OnPostFunc onPost, void* onPostContext)
+{
+}
+
 void android_getOpenglesHardwareStrings(char* vendor, size_t vendorBufSize,
                                        char* renderer, size_t rendererBufSize,
                                        char* version, size_t versionBufSize)