meson: build nouveau (gallium) driver

Tested with a GK107.

v2: - Add target for nouveau standalone compiler. This target is not
      built by default.
v3: - Add nouveau to list of drivers built by default

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Eric Anholt <eric at anholt.net>
6 files changed