kernel: fix module dependency checking

Since the kernel makefile is using .ONESHELL, we need to add -e to
.SHELLFLAGS so errors are not ignored.

Signed-off-by: Matthias Schiffer <[email protected]>

package/kernel/linux/Makefile

@@ -19,6 +19,7 @@ PKG_LICENSE_FILES:=
 
 export SHELL:=/bin/sh
 .ONESHELL:
+.SHELLFLAGS = -ec
 
 include $(INCLUDE_DIR)/package.mk