Support a "platform-only" version tag.

We tried to support this by version name convention (foo_PLATFORM and
foo_PRIVATE), but not everything follows those conventions. libm has
a LIBC_DEPRECATED, which is a bit to generic to apply this convention
to.

Support a "platform-only" tag which omits the tagged version in the
NDK.

Test: nose2
Bug: None
Change-Id: Iba34628ea02a813d22c8b32d10e54064f17ac6df
diff --git a/cc/test_gen_stub_libs.py b/cc/test_gen_stub_libs.py
index 8436a48..2c79ded 100755
--- a/cc/test_gen_stub_libs.py
+++ b/cc/test_gen_stub_libs.py
@@ -110,6 +110,9 @@
         self.assertTrue(gsl.should_omit_version('foo_PRIVATE', [], 'arm', 9))
         self.assertTrue(gsl.should_omit_version('foo_PLATFORM', [], 'arm', 9))
 
+        self.assertTrue(gsl.should_omit_version(
+            'foo', ['platform-only'], 'arm', 9))
+
     def test_omit_arch(self):
         self.assertFalse(gsl.should_omit_version('foo', [], 'arm', 9))
         self.assertFalse(gsl.should_omit_version('foo', ['arm'], 'arm', 9))