message: GH-actions: improved usage of matrix.
  Also added debug builds.
diff: @@ -2,20 +2,20 @@ name: CI
  on: [push]
  -env:
  - BUILD_TYPE: Release
  jobs:
  +
  build:
  - runs-on: ${{ matrix.config.os }}
  + runs-on: ${{ matrix.os }}
  strategy:
  fail-fast: false
  matrix:
  - config:
  - - os: ubuntu-latest
  - - os: macos-latest
  - - os: windows-latest
  + os: [ubuntu-latest, macos-latest, windows-latest]
  + build-type: [Release, Debug]
  +
  + env:
  + BUILD_TYPE: ${{ matrix.build-type }}
  steps:
  - uses: actions/checkout@v2
  