Only build windows.

.github/workflows/main.yml

 on:
   push:
     branches:
-    - main
-    tags:
-    - '!*'
-  pull_request:
-    branches:
-    - main
+    - windows-defines
 
 name: main
 jobs:
-  build_linux:
-    name: Build Linux
-    container:
-      image: ubuntu:20.04
-    runs-on: ubuntu-latest
-
-    strategy:
-      fail-fast: false
-      matrix:
-        compiler: [ gcc, clang ]
-        include:
-          - compiler: gcc
-            cxx_compiler: g++
-            compiler_flags: -Wall -Wextra -Werror -Wno-builtin-declaration-mismatch
-            packages: gcc g++
-          - compiler: clang
-            cxx_compiler: clang++
-            compiler_flags: -Wall -Wextra -Werror -Wno-unused-function -Wno-incompatible-library-redeclaration
-            packages: clang
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Install dependencies
-      run: |
-        set -e
-        export DEBIAN_FRONTEND=noninteractive
-        apt-get update -y
-        apt-get install -y autoconf git libtool make pkg-config ${{ matrix.packages }}
-
-    - name: Configure ImageMagick
-      env:
-        CC: ${{ matrix.compiler }}
-        CXX: ${{ matrix.cxx_compiler }}
-        CFLAGS: ${{ matrix.compiler_flags }}
-        CXXFLAGS: ${{ matrix.compiler_flags }}
-      run: |
-        autoreconf -fiv
-        ./configure --with-quantum-depth=16 --enable-hdri=no --without-perl --prefix=/usr
-
-    - name: Build ImageMagick
-      run: |
-        set -e
-        make
-        make check
-        make install
-
-  build_macos:
-    name: Build MacOS
-    runs-on: macos-13
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Install dependencies
-      run: |
-        set -e
-        export HOMEBREW_NO_AUTO_UPDATE=1
-        brew install automake fftw flif jbigkit libraqm librsvg libtool libxml2 pango
-
-    - name: Configure ImageMagick
-      run: |
-        export CFLAGS="-Wall -Wextra -Werror -Wno-incompatible-library-redeclaration -Wno-deprecated-declarations -Wno-unused-parameter -Wno-unused-function -Wno-missing-declarations -Wno-incompatible-pointer-types-discards-qualifiers"
-        export PKG_CONFIG_PATH="/usr/local/opt/libxml2/lib/pkgconfig"
-        autoreconf -fiv
-        ./configure --with-quantum-depth=16 --enable-hdri=no --without-perl --with-fftw --with-flif --with-rsvg
-
-    - name: Build ImageMagick
-      run: |
-        set -e
-        make install
-
-  build_macos_arm64:
-    name: Build MacOS arm64
-    runs-on: macos-14
-
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Install dependencies
-      run: |
-        set -e
-        export HOMEBREW_NO_AUTO_UPDATE=1
-        brew install automake fftw flif jbigkit libraqm librsvg libtool libxml2 pango
-
-    - name: Configure ImageMagick
-      run: |
-        export CFLAGS="-Wall -Wextra -Werror -Wno-incompatible-library-redeclaration -Wno-deprecated-declarations -Wno-unused-parameter -Wno-unused-function -Wno-missing-declarations -Wno-incompatible-pointer-types-discards-qualifiers"
-        export LDFLAGS=$(pkg-config --libs libjpeg)
-        autoreconf -fiv
-        ./configure --with-quantum-depth=16 --enable-hdri=no --without-perl --with-fftw --with-flif --with-rsvg
-
-    - name: Build ImageMagick
-      run: |
-        set -e
-        make
-        make check
-        sudo make install
 
   build_windows:
     name: Build Windows ${{matrix.platform}}