[SKIP CI] Revert "Parallelize parts of PR build check workflow"

This reverts commit e5acb018b8.

.github/workflows/build_pull_request.yml

@@ -15,8 +15,8 @@ jobs:
       - name: Validate Gradle Wrapper
         uses: gradle/wrapper-validation-action@v1
 
-  build_multisrc_extensions:
-    name: Build multi-source extensions
+  build:
+    name: Build extension repo
     needs: check_wrapper
     if: "!startsWith(github.event.head_commit.message, '[SKIP CI]')"
     runs-on: ubuntu-latest
@@ -51,26 +51,6 @@ jobs:
           dependencies-cache-enabled: true
           configuration-cache-enabled: true
 
-  build_regular_extensions:
-    name: Build regular extensions
-    needs: check_wrapper
-    if: "!startsWith(github.event.head_commit.message, '[SKIP CI]')"
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Checkout PR
-        uses: actions/checkout@v2
-
-      - name: Set up JDK 1.8
-        uses: actions/setup-java@v1
-        with:
-          java-version: 1.8
-
-      - name: Copy CI gradle.properties
-        run: |
-          mkdir -p ~/.gradle
-          cp .github/runner-files/ci-gradle.properties ~/.gradle/gradle.properties
-
       - name: Build extensions
         uses: eskatos/gradle-command-action@v1
         with: