Without this include, CTest can still be run. Removing this cleans up MSVC
solution explorer, as CTestDashboardTargets (Continuous, Experimental,
Nightly and NightlyMemoryCheck) no longer show up

Make it a little more clear how steps correspond, and add 'build'
to both workflow names so the intention of the runs is explicit
on the actions page.

This only runs on linux and macOS, but supports the important
`distcheck` target.

We ask homebrew to install libtool and pkg-config on macOS.
These are required for the autotools build, but aclocal
at least seems not to be available in the latest image.

We don't do a general homebrew update since that can take several
minutes, at least doubling the time it takes to runthhe job.
Just using the defaults the image provides is a better tradeoff.

Run cmake build and test steps on the three supported desktop
targets. Default compiler and so on is fine.

Although we define an environment variable to hold the path
to the cmake build directory, we must use the noisier expression
syntax of the github job builder to substitute into each
command line for portability across both unix and windows
shell syntax.

The windows image also requires an explicit build config
switch, `-C Debug` or similar, for ctest to execute even
though CMakeLists.txt doesn't define alternate build
configurations. On linux and macos ctest runs fine without
the extra argument.

These should match http://downloads.xiph.org/releases/ogg/SHA256SUMS

Result of running `make -C doc/libogg update-doc-version`.