add g++-6 to ubuntu-14.04 (#1144)

* add g++-6 to ubuntu-14.04

* fix syntax

* fix yamllint errors for build-and-test

* fix 'add-apt-repository' command not found

* make 'run tests' explicit

* enable testing and run both release and debug

* oops

.github/workflows/build-and-test.yml

@@ -7,7 +7,8 @@ on:
     branches: [master]
 
 jobs:
-  # TODO: add 32-bit builds (g++ and clang++) for ubuntu (requires g++-multilib and libc6:i386)
+  # TODO: add 32-bit builds (g++ and clang++) for ubuntu
+  #   (requires g++-multilib and libc6:i386)
   # TODO: add coverage build (requires lcov)
   # TODO: add clang + libc++ builds for ubuntu
   # TODO: add clang + ubsan/asan/msan + libc++ builds for ubuntu
@@ -63,12 +64,29 @@ jobs:
       matrix:
         build_type: ['Release', 'Debug']
         compiler: [g++-4.8, clang++-3.6]
+        include:
+          - compiler: g++-6
+            build_type: 'Debug'
+            run_tests: true
+          - compiler: g++-6
+            build_type: 'Release'
+            run_tests: true
     container: ubuntu:14.04
     steps:
       - uses: actions/checkout@v2
 
       - name: install required bits
-      run: sudo apt update && sudo apt -y install clang-3.6 cmake3 g++-4.8 git
+        run: |
+          sudo apt update
+          sudo apt -y install clang-3.6 cmake3 g++-4.8 git
+
+      - name: install other bits
+        if: ${{ matrix.compiler }} == g++-6
+        run: |
+          sudo apt -y install software-properties-common
+          sudo add-apt-repository -y "ppa:ubuntu-toolchain-r/test"
+          sudo apt update
+          sudo apt -y install g++-6
 
       - name: create build environment
         run: cmake -E make_directory $GITHUB_WORKSPACE/_build
@@ -80,17 +98,17 @@ jobs:
         working-directory: ${{ github.workspace }}/_build
         run: >
           cmake $GITHUB_WORKSPACE
-        -DBENCHMARK_ENABLE_TESTING=off
+          -DBENCHMARK_ENABLE_TESTING=${{ matrix.run_tests }}
           -DCMAKE_BUILD_TYPE=${{ matrix.build_type }}
-        #-DBENCHMARK_DOWNLOAD_DEPENDENCIES=ON
+          -DBENCHMARK_DOWNLOAD_DEPENDENCIES=${{ matrix.run_tests }}
 
       - name: build
         shell: bash
         working-directory: ${{ github.workspace }}/_build
         run: cmake --build . --config ${{ matrix.build_type }}
 
-      # - name: test
-      #   shell: bash
-      #   working-directory: ${{ github.workspace }}/_build
-      #   run: ctest -C ${{ matrix.build_type }} -VV
-
+      - name: test
+        if: ${{ matrix.run_tests }}
+        shell: bash
+        working-directory: ${{ github.workspace }}/_build
+        run: ctest -C ${{ matrix.build_type }} -VV