scripts/link-vmlinux.sh: source variables from KCONFIG_CONFIG

Its possible to superseed the config file with KCONFIG_CONFIG and have
completely no .config in the tree. The current script is sourcing
.config in every case, so the kernel will never build succesfully. This
patch fixes that issue by sourcing KCONFIG_CONFIG instead.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index b3d907e..e62f1e0 100644
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -132,7 +132,7 @@
 fi
 
 # We need access to CONFIG_ symbols
-. ./.config
+. ${KCONFIG_CONFIG}
 
 #link vmlinux.o
 info LD vmlinux.o