kbuild: fix build ID symlinks to installed debug VDSO files

Commit 56769ba4 ("kbuild: unify vdso_install rules") accidentally
dropped the '.debug' suffix from the build ID symlinks.

Fixes: 56769ba4 ("kbuild: unify vdso_install rules")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.vdsoinst

@@ -22,7 +22,7 @@ $$(dest): $$(src) FORCE
 
 # Some architectures create .build-id symlinks
 ifneq ($(filter arm sparc x86, $(SRCARCH)),)
-link := $(install-dir)/.build-id/$$(shell $(READELF) -n $$(src) | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p')
+link := $(install-dir)/.build-id/$$(shell $(READELF) -n $$(src) | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p').debug
 
 __default: $$(link)
 $$(link): $$(dest) FORCE