The OSX environment does not have automake installed by default

pkg-config was missing, so the generated configure script was missing how to handle PKG_CHECK_EXISTS() marcros

One of the cli tools on OSX does not support the same
arguments as on Linux. As a result, the prerelease target
fails when building documentation. The prerelease check
will still run on Linux.

There was an option to enable/disable Check's timeout unit tests with autotools.
There was no such option for CMake, and the timeout tests were run unconditionally.

On some systems, such as overloaded computers or VMs, some of the timeout tests
which have smaller timeout values sporadically fail. The option to disable the timeout
tests on such machines will be important to reduce false positives.

The timeout tests have a few tests that use quick
timeouts to check correctness. On machines that are
overloaded or are shared these timeouts may be missed,
causing the tests to fail sporadically.

This commit removes the timeout tests from running on
OSX machines in GitHub Actions, as they sporadically
fail on the quick timeout values. This issue has not been
seen on the Linux Action machines yet, and will stay 
enabled.

This one was missed in the previous commit

This splits the tests into more modular units, so that
the tests run faster overall (are parallelized) and it
will be more obvious what failed when something
goes wrong.

This installs the scan-build utility before using it
in the Actions job.

Reference:
https://github.com/mgrebenets/homebrew-scan-build

Previously the job attempted to use brew to install
scan-build, which would only work on OSX.

For now, backing out changes related to scan-build.
Getting it working will be put off for later.

This reverts commit 80353e7.

For now, backing out changes related to scan-build.
Getting it working will be put off for later.

This reverts commit 9ec47ca.

For now, backing out changes related to scan-build.
Getting it working will be put off for later.

This reverts commit 5d0d87c.