.github/workflows/ndk.yml: add workflow for NDK build

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>

.github/workflows/ndk.yml

@@ -0,0 +1,13 @@
+name: Build against NDK
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: CMake and NDK
+      run: cmake -B build -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake && cmake --build build