Refactor check job to allow configuring CI host runner

.github/workflows/build.yaml

@@ -27,7 +27,7 @@ on:
 jobs:
  check:
  name: Type checking (${{ matrix.target.name }})
- runs-on: ubuntu-latest
+ runs-on: ${{ matrix.target.host }}
  if: ${{ (github.event_name == 'pull_request' && github.event.pull_request.head.repo.fork) || github.event_name == 'push' }}
  strategy:
  matrix:
@@ -36,14 +36,19 @@ jobs:
  # triple: x86_64-pc-windows-gnu
  - name: Linux
  triple: x86_64-unknown-linux-gnu
+ host: ubuntu-latest
  - name: Android
  triple: aarch64-linux-android
+ host: ubuntu-latest
  - name: macOS
  triple: x86_64-apple-darwin
+ host: macos-latest
  - name: iOS
  triple: aarch64-apple-ios
+ host: macos-latest
  - name: FreeBSD
  triple: x86_64-unknown-freebsd
+ host: ubuntu-latest
 
  steps:
  - name: Checkout sources