ci: tidy-ups

- http3-linux: add newlines for readability.
- http3-linux: use `make pytest` to run pytest.
- checksrc: use `|` multiline to sync with other uses.
- checksrc: prefer `$()`.
- prefer `>-` over `>` for folded option lists.
- cygwin: drop a `grep` no longer necessary.

Closes #15081

.github/workflows/cygwin.yml

@@ -166,7 +166,7 @@ jobs:
         if: ${{ matrix.build == 'cmake' }}
         timeout-minutes: 1
         run: |
-          find . -name '*.exe' -o -name '*.dll' | grep -v '/examples/'
+          find . -name '*.exe' -o -name '*.dll'
           PATH="$PWD/bld/lib:$PATH"
           bld/src/curl.exe --disable --version