build-unit-test-docker: Don't download subprojects for meson
build-unit-test-docker: Don't download subprojects for meson

We want to ensure we aren't bundling and duplicating dependencies for
our built-in libraries.

Change-Id: I81c3a51d91de24f1dd76e609f8cc52fb57ea6844
Signed-off-by: William A. Kennington III <30fff5198f4d10ca1117e5f3ec82f3b4b8900d81@google.com>

openbmc/openbmc-build-scripts,openbmc/openbmc-build-scripts