[source] wireguard: move to kernel build directory

[LEDE Commits]

dedeckeh pushed a commit to source.git, branch lede-17.01:
https://git.lede-project.org/8751bd771d8ade9c15519e5ee869a57a3bd67e41

commit 8751bd771d8ade9c15519e5ee869a57a3bd67e41
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Sat Nov 11 13:01:50 2017 +0100

    wireguard: move to kernel build directory
    
    It builds a kernel module, so its build dir should be target specific
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 package/network/services/wireguard/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/network/services/wireguard/Makefile b/package/network/services/wireguard/Makefile
index 8a1e310..9c0e075 100644
--- a/package/network/services/wireguard/Makefile
+++ b/package/network/services/wireguard/Makefile
@@ -21,7 +21,7 @@ PKG_HASH:=d9347786a9406ac276d86321ca64aadb1f0639cb0582c6e0519c634cf6e81157
 PKG_LICENSE:=GPL-2.0 Apache-2.0
 PKG_LICENSE_FILES:=COPYING
 
-PKG_BUILD_DIR:=$(BUILD_DIR)/WireGuard-$(PKG_VERSION)
+PKG_BUILD_DIR:=$(KERNEL_BUILD_DIR)/WireGuard-$(PKG_VERSION)
 PKG_BUILD_PARALLEL:=1
 PKG_USE_MIPS16:=0