Add github actions build

.github/workflows/build.yaml

@@ -0,0 +1,24 @@
+name: Build TDLib
+
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '0 0 * * 0' # weekly
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: "recursive"
+      - name: Install build tools
+        run: sudo apt-get install make git zlib1g-dev libssl-dev gperf php cmake clang-10 libc++-dev libc++abi-dev
+      - name: Build
+        run: |
+          mkdir build
+          cd build
+          CXXFLAGS="-stdlib=libc++" CC=/usr/bin/clang-10 CXX=/usr/bin/clang++-10 cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX:PATH=../tdlib ..
+          cmake --build . --target install