Use exact version of NDK needed by presubmit in Github Actions

It is required to install ninja manually due to it not being included in
the virtual env provided by Github Actions runner.

See actions/runner-images#741

In order for Ninja to be visible to CMake during NDK builds, it must be
installed in the same subdirectory, so for now it is symlinked on Linux
builds. See b/206099937

Fixes: 216535050
Test: Github CI
Change-Id: I1a741b1765822f0004adc3985b7babc8022046a5

.github/workflows/presubmit.yml

@@ -173,16 +173,35 @@ jobs:
         uses: actions/setup-java@v1
         with:
           java-version: "11"
+      # Required for CMake when building workmanager.
+      - name: "Install Ninja"
+        run: |
+          set -x
+          if [ "$RUNNER_OS" == "Linux" ]; then
+            # Should use version 1.10.2 but it is not available on apt yet.
+            sudo apt-get install ninja-build=1.10.0-1build1
+          elif [ "$RUNNER_OS" == "macOS" ]; then
+            # Should use version 1.10.2, but it is not well supported by Homebrew.
+            brew install ninja
+          elif [ "$RUNNER_OS" == "Windows" ]; then
+            choco install ninja --version=1.10.2
+          else
+            echo "Failed to install ninja due to unsupport OS: $RUNNER_OS"
+            exit 1
+          fi
+          # See b/206099937. Hack needed to make ninja visible to cmake during NDK builds
+          if [ ! -e "/usr/local/bin/ninja" ]; then
+            ln -s "/usr/bin/ninja" "/usr/local/bin/ninja"
+          fi
 
       - name: "Set environment variables"
         shell: bash
         run: |
           set -x
           echo "DIST_DIR=$HOME/dist" >> $GITHUB_ENV
-          
-          # use latest NDK because the default NDK on github is older.
-          # TODO b/216535050: Implement task to install the exact AndroidX ndk version.
-          echo "ANDROID_NDK_ROOT=$ANDROID_NDK_LATEST_HOME" >> $GITHUB_ENV
+          # TODO b/216535050: Implement task to install the exact AndroidX ndk
+          # version in case it is not available.
+          echo "ANDROID_NDK_ROOT=$ANDROID_SDK_ROOT/ndk/23.1.7779620" >> $GITHUB_ENV
 
       - name: "Setup Gradle"
         uses: gradle/gradle-build-action@v2