fix(build): sourceMaps updated to support CJS properly again

Fixes #2934

Author: jasonaden

package.json

@@ -82,7 +82,7 @@
     "clean_dist_esm2015": "shx rm -rf ./dist/esm2015",
     "clean_dist_global": "shx rm -rf ./dist/global",
     "commit": "git-cz",
-    "compile_dist_cjs": "tsc   ./dist/src/Rx.ts ./dist/src/add/observable/of.ts ./dist/src/operator/toPromise.ts -m commonjs --lib es5,es2015.iterable,es2015.collection,es2015.promise,dom --sourceMap --outDir ./dist/cjs   --target ES5    --diagnostics --pretty --noImplicitAny --noImplicitReturns --noImplicitThis --suppressImplicitAnyIndexErrors --moduleResolution node -d --declarationDir ./dist/typings",
+    "compile_dist_cjs": "tsc   ./dist/src/Rx.ts ./dist/src/add/observable/of.ts ./dist/src/operator/toPromise.ts -m commonjs --lib es5,es2015.iterable,es2015.collection,es2015.promise,dom --sourceMap --sourceRoot ./src --outDir ./dist/cjs   --target ES5    --diagnostics --pretty --noImplicitAny --noImplicitReturns --noImplicitThis --suppressImplicitAnyIndexErrors --moduleResolution node -d --declarationDir ./dist/typings",
     "compile_dist_esm5": "tsc  ./dist/src/Rx.ts ./dist/src/add/observable/of.ts ./dist/src/operator/toPromise.ts -m es2015   --lib es5,es2015.iterable,es2015.collection,es2015.promise,dom --sourceMap --outDir ./dist/esm5  --target ES5    --diagnostics --pretty --noImplicitAny --noImplicitReturns --noImplicitThis --suppressImplicitAnyIndexErrors --moduleResolution node",
     "compile_dist_esm2015": "tsc ./dist/src/Rx.ts ./dist/src/add/observable/of.ts ./dist/src/operator/toPromise.ts -m es2015   --lib es5,es2015.iterable,es2015.collection,es2015.promise,dom --sourceMap --outDir ./dist/esm2015 --target es2015 --diagnostics --pretty --noImplicitAny --noImplicitReturns --noImplicitThis --suppressImplicitAnyIndexErrors --moduleResolution node",
     "compile_dist_esm2015_for_docs": "tsc ./dist/src/Rx.ts ./dist/src/add/observable/of.ts ./dist/src/MiscJSDoc.ts ./dist/src/operator/toPromise.ts -m es2015   --sourceMap --outDir ./dist/es6 --target es2015 -d --diagnostics --pretty --noImplicitAny --noImplicitReturns --noImplicitThis --suppressImplicitAnyIndexErrors --moduleResolution node",