Stop pinning; keep skipping -U for PyPA; instrument with -vvv

This won't fix it but is diagnostic, to reveal the URL for the
coverage package, so I can see what happens when that is installed
more manually.

Author: EliahKagan

.github/workflows/cygwin-test.yml

@@ -30,7 +30,7 @@ jobs:
     - name: Install Cygwin
       uses: cygwin/cygwin-install-action@v4
       with:
-        packages: python39 python39-virtualenv git
+        packages: python39 python39-pip python39-virtualenv git
         add-to-path: false  # No need to change $PATH outside the Cygwin environment.
 
     - name: Arrange for verbose output
@@ -55,13 +55,14 @@ jobs:
         # and cause subsequent tests to fail
         cat test/fixtures/.gitconfig >> ~/.gitconfig
 
-    - name: Pin pip
+    - name: Ensure the "pip" command is available
       run: |
-        python -m pip install pip==23.3.1
+        # This is used unless, and before, an updated pip is installed.
+        ln -s pip3 /usr/bin/pip
 
     - name: Install project and test dependencies
       run: |
-        python -m pip install ".[test]"
+        pip -vvv install ".[test]"
 
     - name: Show version and platform information
       run: |