build: speedup test.untit.dart by removing unneeded pub symlinks

This is an alternative to #2778. All of the symlinks to packages directory within the test directory
are not needed for running tests, so we can safely remove them. This removes 80k files from the test directory
which significantly speeds up Karma.

Closes #2437

gulpfile.js

@@ -208,6 +208,31 @@ gulp.task('build/pubspec.dart', pubget.subDir(gulp, gulpPlugins, {
   command: DART_SDK.PUB
 }));
 
+
+// This is a hacky way to work around dart's pub that creates `packages` symlink in every directory
+// that contains a dart file with the main method. For our tests this means that every test subfolder
+// has a link to the root `packages` directory which causes Karma to sift through 80k files during
+// each `karma run` invocation.
+//
+// Since these directories are not needed for karma tests to run, it's safe to delete them without
+// breaking any functionality.
+//
+// See #2437 for more info.
+gulp.task('!build/remove-pub-symlinks', function(done) {
+  if (process.platform == 'win32') {
+    done();
+    return;
+  }
+
+  exec('find dist/dart/angular2/test/ -name packages | xargs rm -r', function (error, stdout, stderr) {
+    if (error) {
+      done(stderr);
+      return;
+    }
+    done();
+  });
+});
+
 // ------------
 // dartanalyzer
 
@@ -480,6 +505,7 @@ gulp.task('test.unit.dart', function (done) {
     'build/tree.dart',
     '!build/pubget.angular2.dart',
     '!build/change_detect.dart',
+    '!build/remove-pub-symlinks',
     '!test.unit.dart/karma-server',
     '!test.unit.dart/karma-run',
     function(error) {