Fix compatilibity with Clang-18
https://github.com/ROCm/ROCm-Device-Libs/issues/96

Backports https://github.com/ROCm/llvm-project/commit/688c78d85caf499957db175811f8b00c7c818f83
--- a/ockl/src/cg.cl
+++ b/ockl/src/cg.cl
@@ -84,13 +84,13 @@ multi_grid_sync(__global struct mg_sync *s, uint members)
     }
 }
 
-void
+__attribute__((target("gws"))) void
 __ockl_gws_init(uint nwm1, uint rid)
 {
     __builtin_amdgcn_ds_gws_init(nwm1, rid);
 }
 
-void
+__attribute__((target("gws"))) void
 __ockl_gws_barrier(uint nwm1, uint rid)
 {
     __builtin_amdgcn_ds_gws_barrier(nwm1, rid);