targets/gbm: exit gracefully if pipe_loader_drm_probe_fd is not available

When one builds without gallium_drm_loader, the above function will
not be available, thus we'll segfault in gallium_screen_create due
to memory access violation.

Tested-by: Tom Stellard <thomas.stellard@amd.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75335
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
1 file changed