Error if vendor apex adds an LLNDK library

This is a common mistake when creating a vendor apex. They often try to
list all dependencies. Adding an LLNDK results in putting a stub library
in APEX, which simply doesn't work.

This change prevents stubs from being added to APEX.

Bug: 314033460
Test: go test ./apex
Change-Id: Ic3365047028d9ab6f06992d52aece5a3890177bb

apex/apex_test.go

@@ -26,6 +26,7 @@ import (
 	"testing"
 
 	"android/soong/aconfig/codegen"
+
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 
@@ -960,6 +961,32 @@ func TestApexWithStubs(t *testing.T) {
 	ensureListContains(t, names(apexManifestRule.Args["requireNativeLibs"]), "libfoo.shared_from_rust.so")
 }
 
+func TestApexShouldNotEmbedStubVariant(t *testing.T) {
+	testApexError(t, `module "myapex" .*: native_shared_libs: "libbar" is a stub`, `
+		apex {
+			name: "myapex",
+			key: "myapex.key",
+			vendor: true,
+			updatable: false,
+			native_shared_libs: ["libbar"], // should not add an LLNDK stub in a vendor apex
+		}
+
+		apex_key {
+			name: "myapex.key",
+			public_key: "testkey.avbpubkey",
+			private_key: "testkey.pem",
+		}
+
+		cc_library {
+			name: "libbar",
+			srcs: ["mylib.cpp"],
+			llndk: {
+				symbol_file: "libbar.map.txt",
+			}
+		}
+	`)
+}
+
 func TestApexCanUsePrivateApis(t *testing.T) {
 	ctx := testApex(t, `
 		apex {