Don't strip stub libraries

LLNDK and NDK stubs are already not stripped, don't strip APEX stubs
either.

Test: m checkbuild
Change-Id: I9a50df4b8b73d764ca81634a8a3014726eceda99
diff --git a/cc/library.go b/cc/library.go
index 11ee7dd..d5c9131 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -977,7 +977,12 @@
 	transformSharedObjectToToc(ctx, outputFile, tocFile, builderFlags)
 
 	stripFlags := flagsToStripFlags(flags)
-	if library.stripper.NeedsStrip(ctx) {
+	needsStrip := library.stripper.NeedsStrip(ctx)
+	if library.buildStubs() {
+		// No need to strip stubs libraries
+		needsStrip = false
+	}
+	if needsStrip {
 		if ctx.Darwin() {
 			stripFlags.StripUseGnuStrip = true
 		}