Automatically enable abi checker for the stub libs

The header ABI checker is enabled by default for the libs that are used
across APEXes.

Bug: 138219814
Test: m
Change-Id: Ic0e9c5fdfa1259f500d990abc504c452436f3bd7
diff --git a/cc/library.go b/cc/library.go
index 6564fa1..52fd346 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -464,7 +464,7 @@
 			}
 		}
 	}
-	if enabled != nil && Bool(enabled) {
+	if Bool(enabled) || ctx.hasStubsVariants() {
 		return "PLATFORM"
 	}
 	return ""
@@ -894,7 +894,7 @@
 		}
 		exportedHeaderFlags := strings.Join(SourceAbiFlags, " ")
 		library.sAbiOutputFile = TransformDumpToLinkedDump(ctx, objs.sAbiDumpFiles, soFile, fileName, exportedHeaderFlags,
-			android.OptionalPathForModuleSrc(ctx, library.Properties.Header_abi_checker.Symbol_file),
+			android.OptionalPathForModuleSrc(ctx, library.symbolFileForAbiCheck(ctx)),
 			library.Properties.Header_abi_checker.Exclude_symbol_versions,
 			library.Properties.Header_abi_checker.Exclude_symbol_tags)
 
@@ -1095,6 +1095,16 @@
 	return library.MutatedProperties.BuildStubs
 }
 
+func (library *libraryDecorator) symbolFileForAbiCheck(ctx ModuleContext) *string {
+	if library.Properties.Header_abi_checker.Symbol_file != nil {
+		return library.Properties.Header_abi_checker.Symbol_file
+	}
+	if ctx.hasStubsVariants() && library.Properties.Stubs.Symbol_file != nil {
+		return library.Properties.Stubs.Symbol_file
+	}
+	return nil
+}
+
 func (library *libraryDecorator) stubsVersion() string {
 	return library.MutatedProperties.StubsVersion
 }