The major reason to do this is that running tests *both* installed
and uninstalled in our CI is a mostly pointless waste of time.
Particularly given we have a few expensive tests.
We *do* have tests that only run uninstalled (since they require
the source code) like `test-symbols.sh`.
Hence, add `--enable-installed-tests=exclusive` to mean *only* do installed for
most tests.
We'll still have uninstalled coverage via the Travis/Debian configs, and we
could perhaps do another build with a subset of uninstalled tests, but I'm not
really concerned about it.
I'd like to do a renewed push for the InstalledTests model since
I feel it's just fundamentally better. (`g-d-t-r` kind of sucks,
but then so does the automake runner).
Also while we're here - fix the CI to use the correct context,
which started this mess.
Closes: #837
Approved by: dbnicholson
c7efe01520