chore(ci) Split the release in several jobs.

The goal is to avoid calling `actions/create-release` more than once,
because it will fail.

.github/workflows/release.yml

@@ -6,8 +6,8 @@ on:
       - '**'
 
 jobs:
-  release:
-    name: Release
+  test:
+    name: Test
 
     strategy:
       matrix:
@@ -61,13 +61,16 @@ jobs:
           export PATH="$HOME/.cargo/bin:$PATH"
           make test
 
-      - name: Create the JAR
-        id: create_jar
-        shell: bash
-        run: |
-          export PATH="$HOME/.cargo/bin:$PATH"
-          make package
+  create_pre_release:
+    name: Release
+
+    needs: [test]
 
+    runs-on: ubuntu-latest
+
+    steps:
+      # The pre-release must be created only once, hence the split
+      # into multiple jobs with different `strategy`.
       - name: Create a Github pre-release
         id: create_pre_release
         uses: actions/create-release@v1
@@ -79,12 +82,58 @@ jobs:
           draft: false
           prerelease: true
 
+      - name: Output `release_url` into a temporary file
+        run: echo "${{ steps.create_pre_release.outputs.upload_url }}" > release_url.txt
+
+      - name: Save the `release_url` temporary file
+        uses: actions/upload-artifact@v1
+        with:
+          name: release_url
+          path: release_url.txt
+
+  publish_jar:
+    name: Publish the JARs
+
+    needs: [create_pre_release]
+
+    strategy:
+      matrix:
+        # The job runs on 3 different OS.
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        # The job runs on different Java versions (LTS).
+        java: [8]
+      # As soon as one job fails in the matrix, all the other
+      # in-progress jobs are canceled.
+      fail-fast: true
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Create the JAR
+        id: create_jar
+        shell: bash
+        run: |
+          export PATH="$HOME/.cargo/bin:$PATH"
+          make package
+
+      - name: Load the `release_url` from the temporary file
+        uses: actions/download-artifact@v1
+        with:
+          name: release_url
+
+      - name: Read the `release_url` temporary file
+        id: get_release_info
+        shell: bash
+        run: |
+          value=$(cat release_url/release_url.txt)
+          echo ::set-output name=upload_url::$value
+
       - name: Upload JAR as Github pre-release asset
         uses: actions/upload-release-asset@v1
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
-          upload_url: ${{ steps.create_pre_release.outputs.upload_url }}
+          upload_url: ${{ steps.get_release_info.outputs.upload_url }}
           asset_path: ${{ steps.create_jar.outputs.path }}
           asset_name: ${{ steps.create_jar.outputs.name }}
           asset_content_type: application/java-archive