fix(@angular/cli): allow build output in outDir outside of project

Author: hansl

packages/@angular/cli/models/webpack-configs/common.ts

@@ -99,11 +99,12 @@ export function getCommonConfig(wco: WebpackConfigOptions) {
       // specify a configuration flag.
       // Also prevent writing outside the project path. That is not overridable.
       const fullOutputPath = path.resolve(buildOptions.outputPath, asset.output);
-      if (!fullOutputPath.startsWith(projectRoot)) {
-        const message = 'An asset cannot be written to a location outside the project.';
-        throw new SilentError(message);
-      }
       if (!fullOutputPath.startsWith(path.resolve(buildOptions.outputPath))) {
+        if (!fullOutputPath.startsWith(projectRoot)) {
+          const message = 'An asset cannot be written to a location outside the project.';
+          throw new SilentError(message);
+        }
+
         if (!asset.allowOutsideOutDir) {
           const message = 'An asset cannot be written to a location outside of the output path. '
                         + 'You can override this message by setting the `allowOutsideOutDir` '