fix(compiler): look for flat module resources using declaration module path (#15367)

`ngc` would look for flat module resources relative to the flat module index.
`ngc` now looks for flat module resources relative to the `.d.ts` file that declarates
the component.

Fixes #15221

PR Close #15367

packages/core/src/reflection/reflection_capabilities.ts

@@ -226,6 +226,8 @@ export class ReflectionCapabilities implements PlatformReflectionCapabilities {
     return `./${stringify(type)}`;
   }
 
+  resourceUri(type: any): string { return `./${stringify(type)}`; }
+
   resolveIdentifier(name: string, moduleUrl: string, members: string[], runtime: any): any {
     return runtime;
   }