fix(schematics): Fix ng add on Windows (#3022)

Need to convert the schematic host path to a windows path. Fixes #3016

Author: jamesdaniels

.github/workflows/test.yml

@@ -139,7 +139,7 @@ jobs:
       matrix:
         os: [ ubuntu-latest ]
         node: ["14"]
-        firebase: ["9", "canary"]
+        firebase: ["9", "canary", "next"]
         firebaseTools: ["9"]
         rxjs: ["7"]
         ng: ["12", "next"]

src/schematics/setup/index.ts

@@ -1,3 +1,4 @@
+import { asWindowsPath, normalize } from '@angular-devkit/core';
 import { SchematicContext, SchematicsException, Tree } from '@angular-devkit/schematics';
 import {
   getWorkspace, getProject, getFirebaseProjectNameFromHost, addEnvironmentEntry,
@@ -115,7 +116,8 @@ export const ngAddSetupProject = (
 ) => async (host: Tree, context: SchematicContext) => {
 
   // TODO is there a public API for this?
-  const projectRoot: string = (host as any)._backend._root;
+  let projectRoot: string = (host as any)._backend._root;
+  if (process.platform.startsWith('win32')) { projectRoot = asWindowsPath(normalize(projectRoot)); }
 
   const features = await featuresPrompt();