Free up additional disk space on GitHub runner

Building with coverage support creates large binaries as well as
coverage records, all of which consume considerable disk space.
2cee3b1 appears to have pushed this over the top for it creates a
library archive consuming another 2.2 GB of disk space.

This additional build step cleans out binaries that we do not need, such
as Haskell, .NET, or Android SDKs. This frees up 28 GB of memory (out of
a total of 84 GB).

.github/workflows/pull-request-checks.yaml

@@ -910,6 +910,12 @@ jobs:
         uses: actions/checkout@v3
         with:
           submodules: recursive
+      - name: Remove unnecessary software to free up disk space
+        run: |
+          # inspired by https://github.com/easimon/maximize-build-space/blob/master/action.yml
+          df -h
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/* /opt/*
+          df -h
       - name: Download testing and coverage dependencies
         env:
           # This is needed in addition to -yq to prevent apt-get from asking for