mesa/main:  Correct alloca() use without #include "c99_alloca.h"

Fixes: d231f955913e3265d9a560b45dba48ea6336ab90 ("mesa: add hw select name stack code path")

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17073>
1 file changed