Turns out we were missing the glapi bits, making it impossible to use get
the function pointers for this extension. Whoops?!
[daniels: Squashed in a618 SkQP fails, presumably caused by these not
being skipped anymore.]
Fixes: 9f5af68995 ("mesa/main: expose `EXT_multi_draw_indirect`")
Reviewed-by: Antonino Maniscalco <antomani103@gmail.com>
Tested-by: Chris Healy <healych@amazon.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33546>