Produce source maps for local typescriptServices build (#41589)

* Enable source maps for typescriptServices local builds

* Alias gulp lkg -> gulp LKG

src/tsconfig-library-base.json

@@ -2,7 +2,6 @@
     "extends": "./tsconfig-base",
     "compilerOptions": {
         "declarationMap": false,
-        "sourceMap":  false,
         "composite": false,
         "incremental":  true,
         "declaration": true,