panfrost: don't always build bifrost_compiler

src/panfrost/shared is shared with lima driver, build
bifrost_compiler for lima driver is meaningless and
get link error when only lima driver is enabled.

So only build bifrost_compiler when configued with:
  meson -Dtools=panfrost

Fixes: ec2a59cd "panfrost: Move non-Gallium files outside of Gallium"
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Part-of: <mesa/mesa!4960>
25 jobs for !4960 with topic/fix-lima-compile in 9 minutes and 16 seconds (queued for 2 seconds)
merge request