[#316] Create builds on GitHub Actions

This generates builds in a well defined environment, which we can sideload for testing.

Both mainnet and testnet “release” variants are created.

Note that signing is done with an insecure placeholder key stored in the repo.

.github/actions/setup/action.yml

@@ -0,0 +1,44 @@
+name: 'Setup Java and Dependency Cache'
+description: "Configures the build environment and caches Gradle and dependencies."
+runs:
+  using: "composite"
+  steps:
+    - name: Set Env
+      shell: bash
+      run: |
+        echo "home=${HOME}" >> "$GITHUB_ENV"
+    - name: Set up Java
+      uses: actions/setup-java@9519cf1382ac8dc61ad461f7f7cb45f033220189
+      with:
+        distribution: 'temurin'
+        java-version: 17
+    - name: Disable Gradle Daemon
+      shell: bash
+      run: |
+        mkdir ~/.gradle
+
+        echo "org.gradle.daemon=false" >> ~/.gradle/gradle.properties
+    - name: Gradle Wrapper Cache
+      id: gradle-wrapper-cache
+      uses: actions/cache@30f413bfed0a2bc738fdfd409e5a9e96b24545fd
+      with:
+        path: ~/.gradle/wrapper
+        key: ${{ runner.os }}-gradle-wrapper-${{ hashFiles(format('{0}{1}', github.workspace, '/gradle/wrapper/gradle-wrapper.properties')) }}
+    - name: Gradle Dependency Cache
+      id: gradle-dependency-cache
+      uses: actions/cache@30f413bfed0a2bc738fdfd409e5a9e96b24545fd
+      with:
+        path: ~/.gradle/caches/modules-2
+        key: ${{ runner.os }}-gradle-deps-${{ hashFiles(format('{0}{1}', github.workspace, '/gradle.properties')) }}
+        restore-keys: |
+          ${{ runner.os }}-gradle-deps
+    - name: Download Gradle
+      if: steps.gradle-wrapper-cache.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        ./gradlew --version
+    - name: Download Dependencies
+      if: steps.gradle-dependency-cache.outputs.cache-hit != 'true'
+      shell: bash
+      run: |
+        ./gradlew dependencies

.github/workflows/build.yml

@@ -0,0 +1,80 @@
+name: Build
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - master
+    paths-ignore:
+      - '.github/ISSUE_TEMPLATE/*'
+      - '.github/PULL_REQUEST_TEMPLATE.md'
+      - 'LICENSE'
+      - 'README.md'
+      - 'docs/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  validate_gradle_wrapper:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout
+        timeout-minutes: 1
+        uses: actions/checkout@a12a3943b4bdde767164f792f33f40b04645d846
+      # Gradle Wrapper validation can be flaky
+      # https://github.com/gradle/wrapper-validation-action/issues/40
+      - name: Gradle Wrapper Validation
+        timeout-minutes: 1
+        uses: gradle/wrapper-validation-action@e6e38bacfdf1a337459f332974bb2327a31aaf4b
+
+  prime_cache:
+    needs: validate_gradle_wrapper
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout
+        timeout-minutes: 1
+        uses: actions/checkout@a12a3943b4bdde767164f792f33f40b04645d846
+      - name: Setup
+        id: setup
+        timeout-minutes: 12
+        uses: ./.github/actions/setup
+
+  release_build:
+    needs: prime_cache
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout
+        timeout-minutes: 1
+        uses: actions/checkout@a12a3943b4bdde767164f792f33f40b04645d846
+      - name: Setup
+        id: setup
+        timeout-minutes: 5
+        uses: ./.github/actions/setup
+      - name: Build
+        timeout-minutes: 20
+        run: |
+          ./gradlew :app:assemble
+      - name: Collect Artifacts
+        timeout-minutes: 1
+        env:
+          ARTIFACTS_DIR_PATH: ${{ format('{0}/artifacts', env.home) }}
+          BINARIES_ZIP_PATH: ${{ format('{0}/artifacts/binaries.zip', env.home) }}
+          MAPPINGS_ZIP_PATH: ${{ format('{0}/artifacts/mappings.zip', env.home) }}
+        run: |
+          mkdir ${ARTIFACTS_DIR_PATH}
+          zip -r ${BINARIES_ZIP_PATH} . -i app/build/outputs/apk/\*/\*.apk app/build/outputs/universal_apk/\*/\*.apk app/build/outputs/bundle/\*/\*.aab
+          zip -r ${MAPPINGS_ZIP_PATH} . -i *app/build/outputs/mapping/*/mapping.txt
+      - name: Upload Artifacts
+        uses: actions/upload-artifact@6673cd052c4cd6fcf4b4e6e60ea986c889389535
+        timeout-minutes: 1
+        with:
+          name: Release binaries
+          path: ~/artifacts