Use matrix instead of separate jobs in generated CI workflow

[djc]

Currently the generated CI workflow has something like this:

jobs:
  linux:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        target: [x86_64, x86, aarch64, armv7, s390x, ppc64le]
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-python@v4
        with:
          python-version: '3.10'
      - name: Build wheels
        uses: PyO3/maturin-action@v1
        with:
          target: ${{ matrix.target }}
          args: --release --out dist --find-interpreter
          sccache: 'true'
          manylinux: auto
      - name: Upload wheels
        uses: actions/upload-artifact@v3
        with:
          name: wheels
          path: dist

  windows:
    runs-on: windows-latest
    strategy:
      matrix:
        target: [x64, x86]
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-python@v4
        with:
          python-version: '3.10'
          architecture: ${{ matrix.target }}
      - name: Build wheels
        uses: PyO3/maturin-action@v1
        with:
          target: ${{ matrix.target }}
          args: --release --out dist --find-interpreter
          sccache: 'true'
      - name: Upload wheels
        uses: actions/upload-artifact@v3
        with:
          name: wheels
          path: dist

  macos:
    runs-on: macos-latest
    strategy:
      matrix:
        target: [x86_64, aarch64]
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-python@v4
        with:
          python-version: '3.10'
      - name: Build wheels
        uses: PyO3/maturin-action@v1
        with:
          target: ${{ matrix.target }}
          args: --release --out dist --find-interpreter
          sccache: 'true'
      - name: Upload wheels
        uses: actions/upload-artifact@v3
        with:
          name: wheels
          path: dist

The only difference between the different jobs seems to be the use of manylinux: auto? Assuming that that would do the right thing on non-Linux platform, it would be nice to use a matrix instead to use one job that runs over a matrix of platforms and targets. Especially since we can then also set a python variable in the matrix to produce wheels for multiple Python versions.

Here's my adapted version:

  build:
    strategy:
      matrix:
        target: [x86_64]
        python: [3.9, "3.10", "3.11"]
        include:
          - os: ubuntu-latest
            target: x86_64
          - os: windows-latest
            target: x64
          - os: macos-latest
            target: aarch64

    runs-on: ${{ matrix.os }}
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python }}
      - name: Build wheels
        uses: PyO3/maturin-action@v1
        with:
          target: ${{ matrix.target }}
          args: --release --out dist --find-interpreter
          sccache: 'true'
          manylinux: auto
      - name: Upload wheels
        uses: actions/upload-artifact@v3
        with:
          name: wheels
          path: dist

(Personally I think it makes sense to avoid generating binaries for pretty obscure platforms by default.)

[djc]

(So far I'm not actually getting my proposed matrix to work, seems like there's a bug with the matrix setup.)

[davidhewitt]

Closely related to #166