Android: add ci with saving artifacts

.github/workflows/android.yml

@@ -0,0 +1,42 @@
+name: android
+
+# build on c/cpp changes or workflow changes
+on:
+  push:
+    paths:
+      - 'lib/**.[ch]'
+      - 'lib/**.cpp'
+      - 'src/**.[ch]'
+      - 'src/**.cpp'
+      - 'build/android/**'
+      - '.github/workflows/android.yml'
+  pull_request:
+    paths:
+      - 'lib/**.[ch]'
+      - 'lib/**.cpp'
+      - 'src/**.[ch]'
+      - 'src/**.cpp'
+      - 'build/android/**'
+      - '.github/workflows/android.yml'
+
+jobs:
+  build:
+    runs-on: ubuntu-18.04
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 1.8
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.8
+    - name: Build with Gradle
+      run: cd build/android; ./gradlew assemblerelease
+    - name: Save armeabi artifact
+      uses: actions/upload-artifact@v2
+      with:
+        name: Minetest-armeabi-v7a.apk
+        path: build/android/app/build/outputs/apk/release/app-armeabi-v7a-release-unsigned.apk
+    - name: Save arm64 artifact
+      uses: actions/upload-artifact@v2
+      with:
+        name: Minetest-arm64-v8a.apk
+        path: build/android/app/build/outputs/apk/release/app-arm64-v8a-release-unsigned.apk

build/android/app/build.gradle

@@ -11,8 +11,11 @@ android {
 		versionCode project.versionCode
 	}
 
+	// load properties
 	Properties props = new Properties()
-	props.load(new FileInputStream(file('../local.properties')))
+	def propfile = file('../local.properties')
+	if (propfile.exists())
+		props.load(new FileInputStream(propfile))
 
 	if (props.getProperty('keystore') != null) {
 		signingConfigs {