--- gmsl	2020-04-03 18:08:11.000000000 +0800
+++ gmsl	2023-10-22 23:02:05.000000000 +0800
@@ -66,7 +66,7 @@
 # include /foo/gmsl then extract the /foo/ so that __gmsl gets
 # included transparently
 
-__gmsl_root :=
+__gmsl_root := @GMSL_ROOT@
 
 ifneq ($(MAKEFILE_LIST),)
 __gmsl_root := $(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))