Install Pillow directly

.ci/build_cygwin.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+set -e
+
+python3 -m coverage erase
+make clean
+CFLAGS="-coverage -Werror=implicit-function-declaration" python3 -m pip install -v --global-option="build_ext" .
+python3 selftest.py

.ci/install.sh

@@ -13,17 +13,20 @@ aptget_update()
         return 1
     fi
 }
+if [[ $(uname) != CYGWIN* ]]; then
     aptget_update || aptget_update retry || aptget_update retry
+fi
 
 set -e
 
+if [[ $(uname) != CYGWIN* ]]; then
     sudo apt-get -qq install libfreetype6-dev liblcms2-dev python3-tk\
                              ghostscript libffi-dev libjpeg-turbo-progs libopenjp2-7-dev\
                              cmake meson imagemagick libharfbuzz-dev libfribidi-dev
-
     python3 -m pip install --upgrade pip
+fi
+
 python3 -m pip install --upgrade wheel
-PYTHONOPTIMIZE=0 python3 -m pip install cffi
 python3 -m pip install coverage
 python3 -m pip install defusedxml
 python3 -m pip install olefile
@@ -32,6 +35,9 @@ python3 -m pip install -U pytest-cov
 python3 -m pip install -U pytest-timeout
 python3 -m pip install pyroma
 python3 -m pip install test-image-results
+
+if [[ $(uname) != CYGWIN* ]]; then
+    PYTHONOPTIMIZE=0 python3 -m pip install cffi
     python3 -m pip install numpy
 
     # PyQt5 doesn't support PyPy3
@@ -53,3 +59,6 @@ pushd depends && ./install_raqm.sh && popd
 
     # extra test images
     pushd depends && ./install_extra_test_images.sh && popd
+else
+    cd depends && ./install_extra_test_images.sh && cd ..
+fi

.github/workflows/test-cygwin.yml

@@ -41,24 +41,15 @@ jobs:
         run: |
           bash.exe -c "python3 .github/workflows/system-info.py"
 
-      - name: Ensure Python dependencies are installed
+      - name: Install dependencies
         run: |
-          bash.exe -c "python3 -m pip install pip wheel setuptools"
-          bash.exe -c "python3 -m pip install -r requirements.txt"
+          bash.exe .ci/install.sh
 
-      - name: Download extra test images
+      - name: Build
         run: |
-          bash.exe -c "cd depends; dash install_extra_test_images.sh"
+          bash.exe .ci/build_cygwin.sh
 
-      - name: Build Pillow
-        run: |
-          bash.exe -c "python3 setup.py bdist_wheel"
-
-      - name: Install Pillow
-        run: |
-          bash.exe -c "python3 -m pip install dist/*.whl"
-
-      - name: Test Pillow
+      - name: Test
         run: |
           bash.exe xvfb-run -s '-screen 0 1024x768x24' .ci/test.sh