ci: Exclude build tooling (resources/) from coverage

resources/buildConfigDefinitions.js is a build-time codegen tool, not
shipped runtime code. Its generation pipeline only runs on direct
execution (require.main === module), so it can't be exercised by the test
suite, and it only exports mapperFor. Measuring it reports ~19% and drags
the project coverage number down for code that isn't part of the product.
Exclude resources/** from nyc instrumentation.

Author: dblythy

.nycrc

@@ -4,7 +4,8 @@
     "text-summary"
   ],
   "exclude": [
-    "**/spec/**"
+    "**/spec/**",
+    "resources/**"
   ]
 }