add BUILD_NUMBER env - fix issue with downloading dependencies

.github/workflows/maven.yml

@@ -0,0 +1,24 @@
+name: jdk21
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+env:
+  BUILD_NUMBER: 999999
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 21
+      uses: actions/setup-java@v1
+      with:
+        distribution: 'temurin'
+        java-version: 21
+    - name: Build with Maven
+      run: mvn -U -T 1C -Dmaven.javadoc.skip=true -B -V clean package