clean up LD_PRELOAD to prevent warnings while compiling the next build
ERROR: ld.so: object '/mnt/mesa/install/lib/libamdgpu_noop_drm_shim.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
ERROR: ld.so: object '/mnt/mesa/install/lib/libamdgpu_noop_drm_shim.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
ERROR: ld.so: object '/mnt/mesa/install/lib/libamdgpu_noop_drm_shim.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
ERROR: ld.so: object '/mnt/mesa/install/lib/libamdgpu_noop_drm_shim.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
[593/614] Compiling C object src/amd/common/libamd_common.a.p/ac_nir.c.o