pan/bi: Improve unknown intrinsic error

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8358>

src/panfrost/bifrost/bifrost_compile.c

@@ -768,7 +768,8 @@ bi_emit_intrinsic(bi_builder *b, nir_intrinsic_instr *instr)
                 break;
 
         default:
-                unreachable("Unknown intrinsic");
+                fprintf(stderr, "Unhandled intrinsic %s\n", nir_intrinsic_infos[instr->intrinsic].name);
+                assert(0);
         }
 }