util: Getting u_debug not depends on pipe/* files

src/util/* are shared with virgl, and virgl didn't pull pipe/*, so getting u_debug.h independent from pipe/* are necessary to sync src/util/* with virgl/virglrender

The virgl code is at https://gitlab.freedesktop.org/virgl/virglrenderer/-/blob/master/src/mesa/util/u_debug.h

Signed-off-by: Yonggang Luo luoyonggang@gmail.com