Generate aapt Proguard configuration in apk build script

Change-Id: I05a33b1210e6a65b73ad325d328c0005c9c89224
diff --git a/tools/build_sample_apk.py b/tools/build_sample_apk.py
index 5d691d9..e1b2deb 100755
--- a/tools/build_sample_apk.py
+++ b/tools/build_sample_apk.py
@@ -82,7 +82,8 @@
             '-S', 'res',
             '-m',
             '-J', get_gen_path(app),
-            '-F', os.path.join(get_bin_path(app), 'resources.ap_')]
+            '-F', os.path.join(get_bin_path(app), 'resources.ap_'),
+            '-G', os.path.join(get_build_dir(app), 'proguard_options')]
     run_aapt(aapt, args)
 
 def compile_with_javac(api, app):