github: linux workflow

.github/workflows/linux.yml

@@ -0,0 +1,26 @@
+name: linux
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-20.04
+    strategy:
+      fail-fast: false
+      matrix:
+        compiler:
+        - { cc: "gcc-7", cxx: "g++-7" }
+        - { cc: "gcc-8", cxx: "g++-8" }
+        - { cc: "gcc-9", cxx: "g++-9" }
+        - { cc: "gcc-10", cxx: "g++-10" }
+        - { cc: "clang-8", cxx: "clang++-8" }
+        - { cc: "clang-9", cxx: "clang++-9" }
+        - { cc: "clang-10", cxx: "clang++-10" }
+    name: "${{matrix.compiler.cxx}}"
+    steps:
+    - uses: actions/checkout@v2
+    - name: Build
+      run: .ci/build_linux.sh
+      env:
+        CC: ${{matrix.compiler.cc}}
+        CXX: ${{matrix.compiler.cxx}}