remove autotools build system

- TODO: update INSTALL.txt to replace the autotools configure
        instructions with cmake.
- TODO: update make build system to provide an equivalent to
        autotools' `make dist` ?
- TODO: update / revise github actions, replace autotools-only
        ones with cmake (e.g.: vmactions.yml for FreeBSD.)

Reference issue: https://github.com/libsdl-org/SDL/issues/6571

.github/workflows/main.yml

@@ -20,12 +20,9 @@ jobs:
         - { name: Windows (clang32),        os: windows-latest, shell: 'msys2 {0}', msystem: clang32, msys-env: mingw-w64-clang-i686 }
         - { name: Windows (clang64),        os: windows-latest, shell: 'msys2 {0}', msystem: clang64, msys-env: mingw-w64-clang-x86_64 }
         - { name: Windows (ucrt64),         os: windows-latest, shell: 'msys2 {0}', msystem: ucrt64,  msys-env: mingw-w64-ucrt-x86_64 }
-        - { name: Ubuntu 20.04 (CMake),     os: ubuntu-20.04,   shell: sh }
-        - { name: Ubuntu 20.04 (autotools), os: ubuntu-20.04,   shell: sh,    autotools: true }
-        - { name: Ubuntu 22.04 (CMake),     os: ubuntu-22.04,   shell: sh }
-        - { name: Ubuntu 22.04 (autotools), os: ubuntu-22.04,   shell: sh,    autotools: true }
-        - { name: MacOS (CMake),            os: macos-latest,   shell: sh,    cmake: '-DCMAKE_OSX_ARCHITECTURES="x86_64;arm64"' }
-        - { name: MacOS (autotools),        os: macos-latest,   shell: sh,    autotools: true }
+        - { name: Ubuntu 20.04,             os: ubuntu-20.04,   shell: sh }
+        - { name: Ubuntu 22.04,             os: ubuntu-22.04,   shell: sh }
+        - { name: MacOS,                    os: macos-latest,   shell: sh,    cmake: '-DCMAKE_OSX_ARCHITECTURES="x86_64;arm64"' }
 
     steps:
     - name: Set up MSYS2
@@ -63,10 +60,9 @@ jobs:
     - uses: actions/checkout@v3
     - name: Check that versioning is consistent
       # We only need to run this once: arbitrarily use the Linux/CMake build
-      if: "runner.os == 'Linux' && ! matrix.platform.autotools"
+      if: "runner.os == 'Linux'"
       run: ./build-scripts/test-versioning.sh
     - name: Configure (CMake)
-      if: "! matrix.platform.autotools"
       run: |
         cmake -S . -B build -G Ninja \
         -DSDL_TESTS=ON \
@@ -77,11 +73,9 @@ jobs:
         -DCMAKE_BUILD_TYPE=Release \
         ${{ matrix.platform.cmake }}
     - name: Build (CMake)
-      if: "! matrix.platform.autotools"
       run: |
         cmake --build build/ --config Release --verbose --parallel
     - name: Run build-time tests (CMake)
-      if: "! matrix.platform.autotools"
       run: |
         set -eu
         export SDL_TESTS_QUICK=1
@@ -91,76 +85,11 @@ jobs:
           strings build/libSDL3.so.0 | grep SDL-
         fi
     - name: Install (CMake)
-      if: "! matrix.platform.autotools"
       run: |
         set -eu
         cmake --install build/ --config Release
         echo "SDL3_DIR=$(pwd)/cmake_prefix" >> $GITHUB_ENV
         ( cd cmake_prefix; find . ) | LC_ALL=C sort -u
-    - name: Configure (Autotools)
-      if: matrix.platform.autotools
-      run: |
-        set -eu
-        rm -fr build-autotools
-        mkdir build-autotools
-        ./autogen.sh
-        (
-          cd build-autotools
-          ${{ github.workspace }}/configure \
-            --enable-vendor-info="Github Workflow" \
-            --enable-werror \
-            --prefix=${{ github.workspace }}/autotools_prefix \
-        )
-        if test "${{ runner.os }}" != "macOS" ; then
-          curdir="$(pwd)"
-          multiarch="$(dpkg-architecture -qDEB_HOST_MULTIARCH)"
-          (
-            mkdir -p build-autotools/test
-            cd build-autotools/test
-            ${{ github.workspace }}/test/configure \
-              --enable-werror \
-              --x-includes=/usr/include \
-              --x-libraries="/usr/lib/${multiarch}" \
-              --prefix=${{ github.workspace }}/autotools_prefix \
-              SDL_CFLAGS="-I${curdir}/include" \
-              SDL_LIBS="-L${curdir}/build-autotools/build/.libs -lSDL3" \
-              ac_cv_lib_SDL3_ttf_TTF_Init=no \
-              ${NULL+}
-          )
-        fi
-    - name: Build (Autotools)
-      if: matrix.platform.autotools
-      run: |
-        set -eu
-        parallel="$(getconf _NPROCESSORS_ONLN)"
-        make -j"${parallel}" -C build-autotools V=1
-        if test "${{ runner.os }}" != "macOS" ; then
-          make -j"${parallel}" -C build-autotools/test V=1
-        fi
-    - name: Run build-time tests (Autotools)
-      if: ${{ matrix.platform.autotools && (runner.os != 'macOS') }}
-      run: |
-        set -eu
-        curdir="$(pwd)"
-        parallel="$(getconf _NPROCESSORS_ONLN)"
-        export SDL_TESTS_QUICK=1
-        make -j"${parallel}" -C build-autotools/test check LD_LIBRARY_PATH="${curdir}/build-autotools/build/.libs"
-        if test "${{ runner.os }}" = "Linux"; then
-          # This should show us the SDL_REVISION
-          strings "${curdir}/build-autotools/build/.libs/libSDL3.so.0" | grep SDL-
-        fi
-    - name: Install (Autotools)
-      if: matrix.platform.autotools
-      run: |
-        set -eu
-        curdir="$(pwd)"
-        parallel="$(getconf _NPROCESSORS_ONLN)"
-        make -j"${parallel}" -C build-autotools install V=1
-        if test "${{ runner.os }}" != "macOS" ; then
-          make -j"${parallel}" -C build-autotools/test install V=1
-        fi
-        ( cd autotools_prefix; find . ) | LC_ALL=C sort -u
-        echo "SDL3_DIR=$(pwd)/autotools_prefix" >> $GITHUB_ENV
     - name: Verify CMake configuration files
       run: |
         cmake -S cmake/test -B cmake_config_build -G Ninja \
@@ -175,32 +104,3 @@ jobs:
       run: |
         export PKG_CONFIG_PATH=${{ env.SDL3_DIR }}/lib/pkgconfig
         cmake/test/test_pkgconfig.sh
-    - name: Distcheck (Autotools)
-      if: matrix.platform.autotools
-      run: |
-        set -eu
-        parallel="$(getconf _NPROCESSORS_ONLN)"
-        make -j"${parallel}" -C build-autotools dist V=1
-        # Similar to Automake `make distcheck`: check that the tarball
-        # release is sufficient to do a new build
-        mkdir distcheck
-        tar -C distcheck -zxf build-autotools/SDL3-*.tar.gz
-        ( cd distcheck/SDL3-* && ./configure )
-        make -j"${parallel}" -C distcheck/SDL3-*
-    - name: Run installed-tests (Autotools)
-      if: "runner.os == 'Linux' && matrix.platform.autotools"
-      run: |
-        set -eu
-        parallel="$(getconf _NPROCESSORS_ONLN)"
-        sudo make -j"${parallel}" -C build-autotools install
-        sudo make -j"${parallel}" -C build-autotools/test install
-        export SDL_TESTS_QUICK=1
-        # We need to set LD_LIBRARY_PATH because it isn't in the default
-        # linker search path. We don't need to set XDG_DATA_DIRS for
-        # ginsttest-runner, because /usr/local/share *is* in the default
-        # search path for that.
-        env --chdir=/ \
-            LD_LIBRARY_PATH=/usr/local/lib \
-            SDL_AUDIODRIVER=dummy \
-            SDL_VIDEODRIVER=dummy \
-            ginsttest-runner --tap SDL3

.github/workflows/riscos.yml

@@ -12,31 +12,12 @@ jobs:
       fail-fast: false
       matrix:
         platform:
-          - { name: autotools, test_args: '-DTEST_SHARED=FALSE' } # FIXME: autotools should build and install shared libraries
           - { name: CMake }
 
     steps:
     - name: Setup dependencies
       run: apt-get update && apt-get install -y cmake ninja-build
     - uses: actions/checkout@v3
-    - name: Configure (autotools)
-      if: ${{ contains(matrix.platform.name, 'autotools') }}
-      run: |
-        mkdir build_autotools
-        cd build_autotools
-        ../configure \
-          --host=arm-unknown-riscos \
-          --disable-gcc-atomics \
-          --prefix=${{ github.workspace }}/prefix_autotools
-    - name: Build (autotools)
-      if: ${{ contains(matrix.platform.name, 'autotools') }}
-      run: make -C build_autotools -j`nproc` V=1
-    - name: Install (autotools)
-      if: ${{ contains(matrix.platform.name, 'autotools') }}
-      run: |
-        echo "SDL3_DIR=${{ github.workspace }}/prefix_autotools" >> $GITHUB_ENV
-        make -C build_autotools install
-        ( cd ${{ github.workspace }}/prefix_autotools; find ) | LC_ALL=C sort -u
     - name: Configure (CMake)
       if: ${{ contains(matrix.platform.name, 'CMake') }}
       run: |