Handle the case when a symbol is annotated with "# apex vndk"

This change fixes a bug that a symbol is omitted for apex (or vndk) when
it is annotated with "# vndk apex" (or "# apex vndk).

Bug: 123349183
Test: python3 test_gen_stub_libs.py

Change-Id: I344d6e70732bae8877cb16bbe881edb79fe90670
diff --git a/cc/gen_stub_libs.py b/cc/gen_stub_libs.py
index 4906ea2..81bc398 100755
--- a/cc/gen_stub_libs.py
+++ b/cc/gen_stub_libs.py
@@ -119,9 +119,12 @@
         return True
     if 'platform-only' in version.tags:
         return True
-    if 'vndk' in version.tags and not vndk:
-        return True
-    if 'apex' in version.tags and not apex:
+
+    no_vndk_no_apex = 'vndk' not in version.tags and 'apex' not in version.tags
+    keep = no_vndk_no_apex or \
+           ('vndk' in version.tags and vndk) or \
+           ('apex' in version.tags and apex)
+    if not keep:
         return True
     if not symbol_in_arch(version.tags, arch):
         return True
@@ -132,9 +135,11 @@
 
 def should_omit_symbol(symbol, arch, api, vndk, apex):
     """Returns True if the symbol should be omitted."""
-    if not vndk and 'vndk' in symbol.tags:
-        return True
-    if not apex and 'apex' in symbol.tags:
+    no_vndk_no_apex = 'vndk' not in symbol.tags and 'apex' not in symbol.tags
+    keep = no_vndk_no_apex or \
+           ('vndk' in symbol.tags and vndk) or \
+           ('apex' in symbol.tags and apex)
+    if not keep:
         return True
     if not symbol_in_arch(symbol.tags, arch):
         return True