Fixed signature of FrameworkPackageStubs / com.android.car.frameworkpackagestubs

Test: atest CtsSystemIntentTestCases
Fixes: 159154447

Change-Id: Ib29c33987b55b5618a135a455add7b6e78243da1
diff --git a/FrameworkPackageStubs/Android.mk b/FrameworkPackageStubs/Android.mk
index c6a68c8..e24a583 100644
--- a/FrameworkPackageStubs/Android.mk
+++ b/FrameworkPackageStubs/Android.mk
@@ -6,6 +6,8 @@
 LOCAL_PACKAGE_NAME := CarFrameworkPackageStubs
 LOCAL_PRIVATE_PLATFORM_APIS := true
 
+LOCAL_CERTIFICATE := platform
+
 LOCAL_MODULE_TAGS := optional
 
 include $(BUILD_PACKAGE)