Build: Update grunt-contrib-qunit to fix caching of Chromium binary

* Puppeteer stores the Chromium binary only in node_modules/
  (not in $XDG_CACHE_HOME or some other directory that is generally
  persisted in dev and CI environments, nor in any other directory
  that one can opt-in to caching/persistence).

  This was fixed in Puppeteer 5+ (ref puppeteer/puppeteer#6014),
  through an opt-in PUPPETEER_DOWNLOAD_PATH env var.

* I enalbed this in commit 7cd99a2, but it didn't do anything
  yet as grunt-contrib-qunit wasn't using the newer Puppeteer yet.

  This was fixed in gruntjs/grunt-contrib-qunit#173.

* Fix ENV syntax.
  - Tildes aren't expanded in this context.
  - Other variables like $HOME aren't expanded either.
  - Absolute paths like /tmp can't be used because Windows runners interpret
    `/tmp` as `D:\tmp`, which doesn't exist by default, and Puppeteer requires
    the parent dir to exist instead of simply lazy-creating it.
  - Can't use a relative directory in the workspace like ".puppeteer"
    because Puppeteer insists on the variable being an absolute path.
  - We can use the `github.workspace` builtin variable,
    which we can subsitute per <https://git.io/JUJEE>.

.github/workflows/CI.yaml

@@ -43,7 +43,7 @@ jobs:
     name: ${{ matrix.name }}
     runs-on: ${{ matrix.os }}
     env:
-      PUPPETEER_DOWNLOAD_PATH: ~/.puppeteer_download
+      PUPPETEER_DOWNLOAD_PATH: "${{ github.workspace }}/.puppeteer_download"
     steps:
       - uses: actions/checkout@v2
 
@@ -52,7 +52,7 @@ jobs:
         with:
           path: |
             ~/.npm
-            ~/.puppeteer_download
+            ${{ github.workspace }}/.puppeteer_download
           key: ${{ runner.os }}-${{ hashFiles('**/package-lock.json') }}
 
       - name: Use Node.js ${{ matrix.node }}
@@ -86,14 +86,14 @@ jobs:
     name: SpiderMonkey
     runs-on: ubuntu-20.04
     env:
-      PUPPETEER_DOWNLOAD_PATH: ~/.puppeteer_download
+      PUPPETEER_DOWNLOAD_PATH: "${{ github.workspace }}/.puppeteer_download"
     steps:
       - uses: actions/checkout@v2
       - uses: actions/cache@v2
         with:
           path: |
             ~/.npm
-            ~/.puppeteer_download
+            ${{ github.workspace }}/.puppeteer_download
           key: ${{ runner.os }}-${{ hashFiles('**/package-lock.json') }}
       - name: Use Node.js 10
         uses: actions/setup-node@v2

.github/workflows/browsers-full.yaml

@@ -16,15 +16,15 @@ jobs:
     if: ${{ github.repository == 'qunitjs/qunit' }} # skip on forks, needs secret
     runs-on: ubuntu-latest
     env:
-      PUPPETEER_DOWNLOAD_PATH: ~/.puppeteer_download
+      PUPPETEER_DOWNLOAD_PATH: "${{ github.workspace }}/.puppeteer_download"
     steps:
       - uses: actions/checkout@v2
 
       - uses: actions/cache@v2
         with:
           path: |
             ~/.npm
-            ~/.puppeteer_download
+            ${{ github.workspace }}/.puppeteer_download
           key: ${{ runner.os }}-${{ hashFiles('**/package-lock.json') }}
 
       - name: Use Node.js 10

.github/workflows/browsers-quick.yaml

@@ -8,15 +8,15 @@ jobs:
     if: ${{ github.repository == 'qunitjs/qunit' }} # skip on forks, needs secret
     runs-on: ubuntu-latest
     env:
-      PUPPETEER_DOWNLOAD_PATH: ~/.puppeteer_download
+      PUPPETEER_DOWNLOAD_PATH: "${{ github.workspace }}/.puppeteer_download"
     steps:
       - uses: actions/checkout@v2
 
       - uses: actions/cache@v2
         with:
           path: |
             ~/.npm
-            ~/.puppeteer_download
+            ${{ github.workspace }}/.puppeteer_download
           key: ${{ runner.os }}-${{ hashFiles('**/package-lock.json') }}
 
       - name: Use Node.js 10

.github/workflows/coverage.yaml

@@ -8,15 +8,15 @@ jobs:
     if: ${{ github.repository == 'qunitjs/qunit' }} # skip on forks, needs secret
     runs-on: ubuntu-20.04
     env:
-      PUPPETEER_DOWNLOAD_PATH: ~/.puppeteer_download
+      PUPPETEER_DOWNLOAD_PATH: "${{ github.workspace }}/.puppeteer_download"
     steps:
       - uses: actions/checkout@v2
 
       - uses: actions/cache@v2
         with:
           path: |
             ~/.npm
-            ~/.puppeteer_download
+            ${{ github.workspace }}/.puppeteer_download
           key: ${{ runner.os }}-${{ hashFiles('**/package-lock.json') }}
 
       - name: Use Node.js 14

package.json

@@ -66,7 +66,7 @@
     "grunt": "^1.4.1",
     "grunt-contrib-connect": "^3.0.0",
     "grunt-contrib-copy": "^1.0.0",
-    "grunt-contrib-qunit": "^4.0.0",
+    "grunt-contrib-qunit": "^5.0.1",
     "grunt-git-authors": "^3.2.0",
     "grunt-search": "^0.1.8",
     "kleur": "4.1.4",