Update top-level Python project for CMake compatibility.

This commit reimplements the (no longer recommended) setuptools based
build system using a standards-based in-tree PEP517 build backend.
The implementation is partially based on
  https://codeberg.org/ziglang/zig-pypi/src/branch/main/make_wheels.py
which is licensed under BSD-0-clause.

It also adds a new option `YOSYS_BUILD_PYTHON_ONLY` that is available
only if the binary or the library aren't going to be installed, which
turns off these targets entirely, as well as some dependent ones
(e.g. tests).

Co-authored-by: Mohamed Gaber <me@donn.website>

.github/workflows/wheels.yml

@@ -36,13 +36,11 @@ jobs:
               runner: "macos-15",
               archs: "arm64",
             },
-            ## Windows is disabled because of an issue with compiling FFI as
-            ## under MinGW in the GitHub Actions environment (SHELL variable has
-            ## whitespace.)
+            ## Windows still needs to be tested.
             # {
-            #   name: "Windows Server 2019",
+            #   name: "Windows Server 2025",
             #   family: "windows",
-            #   runner: "windows-2019",
+            #   runner: "windows-2025",
             #   archs: "AMD64",
             # },
           ]
@@ -77,17 +75,14 @@ jobs:
         name: "[Windows] Flex/Bison"
         run: |
           choco install winflexbison3
-      - if: ${{ matrix.os.family == 'macos' && matrix.os.archs == 'arm64' }}
-        name: "[macOS/arm64] Install Python 3.8 (see: https://cibuildwheel.pypa.io/en/stable/faq/#macos-building-cpython-38-wheels-on-arm64)"
-        uses: actions/setup-python@v5
-        with:
-          python-version: 3.8
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.21.1
+        uses: pypa/cibuildwheel@v3.4.1
         env:
           # * APIs not supported by PyPy
           # * Musllinux disabled because it increases build time from 48m to ~3h
           CIBW_SKIP: >
+            cp38*
+            cp39*
             pp*
             *musllinux*
           CIBW_ARCHS: ${{ matrix.os.archs }}
@@ -104,7 +99,6 @@ jobs:
             OPTFLAGS=-O3
             PKG_CONFIG_PATH=./ffi/pfx/lib/pkgconfig
             MACOSX_DEPLOYMENT_TARGET=11
-            makeFlags='CONFIG=clang'
             PATH="$PWD/bison/src:$PATH"
           CIBW_BEFORE_BUILD: bash ./.github/workflows/wheels/cibw_before_build.sh
           CIBW_TEST_COMMAND: python3 {project}/tests/pyosys/run_tests.py