chore(build): use inline sources in sourcemaps; don't package sources separately (#6362)

* chore(build): Add inline sources to sourcemaps

* chore(build): Don't package sources

Since the sources are now inline in the sourcemaps, they no longer
need to be package separately.

scripts/gulpfiles/build_tasks.js

@@ -660,23 +660,13 @@ function buildCompiled() {
     // option to Closure Compiler; instead feed them as input via gulp.src.
   };
 
-  // Symlink source dirs from build dir so that sourcemaps work in
-  // compiled-mode testing.
-  for (const src of ['core', 'blocks', 'generators']) {
-    const target = `${BUILD_DIR}/${src}`
-    if (!fs.existsSync(target)) {
-      fs.symlinkSync(`../${src}`, target);
-    }
-  }
-
   // Fire up compilation pipline.
   return gulp.src(chunkOptions.js, {base: './'})
       .pipe(stripApacheLicense())
       .pipe(gulp.sourcemaps.init())
       .pipe(compile(options))
       .pipe(gulp.rename({suffix: COMPILED_SUFFIX}))
-      .pipe(
-          gulp.sourcemaps.write('.', {includeContent: false, sourceRoot: './'}))
+      .pipe(gulp.sourcemaps.write('.'))
       .pipe(gulp.dest(BUILD_DIR));
 }