CI: Parametrize package repos/versions better

.github/workflows/build.yml

@@ -1,4 +1,4 @@
-name: Build
+name: Build packages with Pyodide
 
 on:
   push:
@@ -9,9 +9,11 @@ jobs:
   run_build:
     runs-on: ubuntu-latest
     strategy:
-      matrix:
-        packages: ["https://github.com/Pylons/paginate"]
       fail-fast: false
+      matrix:
+        packages:
+          - {repo: https://github.com/Pylons/paginate, version: "0.5.6"}
+          - {repo: https://github.com/gorakhargosh/watchdog, version: "2.3.1"}
 
     steps:
       - name: Check out the repo
@@ -25,10 +27,8 @@ jobs:
       - name: Define package to build
         run: |
           set -vxeuo pipefail
-          export PACKAGE_SOURCE="${{ matrix.packages }}"
           # https://stackoverflow.com/a/3162500:
-          export PACKAGE_NAME="${PACKAGE_SOURCE##*/}"
-          echo PACKAGE_SOURCE=${PACKAGE_SOURCE} >> $GITHUB_ENV
+          export PACKAGE_NAME="${${{ matrix.packages.repo }}##*/}"
           echo PACKAGE_NAME=${PACKAGE_NAME} >> $GITHUB_ENV
 
       - name: Set up env vars for Emscripten
@@ -47,7 +47,7 @@ jobs:
       - name: Build with Pyodide
         run: |
           set -vxeuo pipefail
-          git clone ${{ env.PACKAGE_SOURCE }}
+          git clone --depth 1 --branch ${{ matrix.packages.version }} ${{ matrix.packages.repo }}
           cd ${{ env.PACKAGE_NAME }}
           pyodide build
           ls -la