unit-test: add meson version check for get_variable

Some repositories are using the newer `get_variable` call in meson
without a keyword argument.  This requires meson 0.58 or later.  I've
contributed fixes for all repositories under the
`meson_deprecated_pkgconfig` topic and so am also adding a CI catch
to prevent future regressions.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9465c3946825ec96d0c934635685e85d74fdf4ee
1 file changed