Build ESM -> CJS before running legacy Node.js tests and packaging tests

Because the source code is written in ESM syntax and we cannot use the
`esm` package to make `require()` ESM compatible, since that package
does not support legacy versions of Node.js.

Also in our usage tests in CI, we need to mimck the npm packaging
behaviour where building is involved.

.github/workflows/usage.yml

@@ -3,15 +3,41 @@ name: Package usage
 on: [push, pull_request]
 
 jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: 14.x
+      - name: npm install and build
+        run: |
+          npm install
+          npm run build
+      - name: Store build-output for later
+        uses: actions/upload-artifact@v2
+        with:
+          name: build-output
+          path: |
+            mustache.js
+            mustache.mjs
+
   package:
     runs-on: ubuntu-latest
 
+    needs: build
     steps:
       - uses: actions/checkout@v2
       - name: Setup Node.js
         uses: actions/setup-node@v1
         with:
           node-version: 14.x
+      - name: Get build-output from build step
+        uses: actions/download-artifact@v2
+        with:
+          name: build-output
       - name: Create package tarball
         run: |
           export ARCHIVE_FILENAME=$(npm pack | tail -n 1)
@@ -71,12 +97,17 @@ jobs:
   browser-usage:
     runs-on: ubuntu-latest
 
+    needs: build
     steps:
       - uses: actions/checkout@v1
       - name: Setup Node.js
         uses: actions/setup-node@v1
         with:
           node-version: 12.x
+      - name: Get build-output from build step
+        uses: actions/download-artifact@v2
+        with:
+          name: build-output
       - name: Install and test
         run: |
           npm ci
@@ -85,10 +116,15 @@ jobs:
   deno-usage:
     runs-on: ubuntu-latest
 
+    needs: build
     steps:
       - uses: actions/checkout@v1
       - uses: denolib/setup-deno@master
         with:
           deno-version: 'v1.0.0'
+      - name: Get build-output from build step
+        uses: actions/download-artifact@v2
+        with:
+          name: build-output
       - run: deno --version
       - run: deno test --allow-net=deno.land test/module-systems/deno-test.ts

.github/workflows/verify.yml

@@ -35,6 +35,27 @@ jobs:
           npm install
           npm run test-unit
 
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: 14.x
+      - name: npm install and build
+        run: |
+          npm install
+          npm run build
+      - name: Store build-output for later
+        uses: actions/upload-artifact@v2
+        with:
+          name: build-output
+          path: |
+            mustache.js
+            mustache.mjs
+
   tests-on-legacy:
     runs-on: ubuntu-latest
 
@@ -42,6 +63,7 @@ jobs:
       matrix:
         node-version: [0.10.x, 0.12.x, 4.x, 6.x, 8.x]
 
+    needs: build
     steps:
       - uses: actions/checkout@v2
         with:
@@ -50,6 +72,10 @@ jobs:
         uses: actions/setup-node@v1
         with:
           node-version: ${{ matrix.node-version }}
+      - name: Get build-output from build step
+        uses: actions/download-artifact@v2
+        with:
+          name: build-output
       - name: npm install and test
         run: |
           npm install mocha@3 chai@3

package.json

@@ -36,7 +36,8 @@
     "pre-test-browser": "node test/create-browser-suite.js",
     "test-browser": "npm run pre-test-browser && zuul -- test/context-test.js test/parse-test.js test/scanner-test.js test/render-test-browser.js",
     "test-browser-local": "npm run pre-test-browser && zuul --local 8080 -- test/context-test.js test/scanner-test.js test/parse-test.js test/render-test-browser.js",
-    "postversion": "scripts/bump-version-in-source"
+    "postversion": "scripts/bump-version-in-source",
+    "prepublishOnly": "npm run build"
   },
   "devDependencies": {
     "chai": "^3.4.0",