symbols in stub library isn't affected by -fvisibility=hidden

Fixing the bug that -fvisibility=hidden in a cc_library is used even
when compiling stub.c file where the symbols shouldn't be hidden.

Bug: 144781653
Test: add folowing to libEGL and build
+    stubs: {
+        symbol_file: "libEGL.map.txt",
+        versions: ["29"],
+    },

Change-Id: Iab70f36a4fb98737fc35827dbc9e1ca1a99d4354

cc/ndk_library.go

@@ -269,6 +269,10 @@ func addStubLibraryCompilerFlags(flags Flags) Flags {
 		// (avoids the need to link an unwinder into a fake library).
 		"-fno-unwind-tables",
 	)
+	// All symbols in the stubs library should be visible.
+	if inList("-fvisibility=hidden", flags.Local.CFlags) {
+		flags.Local.CFlags = append(flags.Local.CFlags, "-fvisibility=default")
+	}
 	return flags
 }