build: fix builds not failing with compilation errors in unit tests (angular#9248)

Fixes the CI continuing to run even though it failed to compile, due to a couple of promises that weren't rejecting properly. This should avoids things like angular#9073 slipping through.

Author: crisbeto

tools/package-tools/build-package.ts

@@ -117,6 +117,7 @@ export class BuildPackage {
     .catch(() => {
       const error = red(`Failed to compile ${secondaryEntryPoint} using ${entryPointTsconfigPath}`);
       console.error(error);
+      return Promise.reject(error);
     });
   }
 

tools/package-tools/compile-entry-point.ts

@@ -33,6 +33,7 @@ export async function compileEntryPoint(buildPackage: BuildPackage, tsconfigName
   .catch(() => {
     const error = red(`Failed to compile ${secondaryEntryPoint} using ${entryPointTsconfigPath}`);
     console.error(error);
+    return Promise.reject(error);
   });
 }