[source] uboot-mvebu: add missing UBOOT_MAKE_FLAGS variable

[LEDE Commits]

hauke pushed a commit to source.git, branch master:
https://git.lede-project.org/ad0e107c2355c8221c96a8cf131405c06c016ae4

commit ad0e107c2355c8221c96a8cf131405c06c016ae4
Author: Marko Ratkaj <marko.ratkaj at sartura.hr>
AuthorDate: Mon Sep 25 12:28:52 2017 +0200

    uboot-mvebu: add missing UBOOT_MAKE_FLAGS variable
    
    This patch removes "/bin/sh: HOSTCPPFLAGS: command not found" errors douring build.
    
    Signed-off-by: Marko Ratkaj <marko.ratkaj at sartura.hr>
---
 package/boot/uboot-mvebu/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/package/boot/uboot-mvebu/Makefile b/package/boot/uboot-mvebu/Makefile
index 2c280fa..b29039c 100644
--- a/package/boot/uboot-mvebu/Makefile
+++ b/package/boot/uboot-mvebu/Makefile
@@ -16,6 +16,8 @@ PKG_HASH:=f54baf3f9325bf444c7905f3a5b6f83680edb1e6e1a4d5f8a5ad80abe885113f
 include $(INCLUDE_DIR)/u-boot.mk
 include $(INCLUDE_DIR)/package.mk
 
+UBOOT_MAKE_FLAGS:=
+
 define U-Boot/Default
   BUILD_TARGET:=mvebu
   HIDDEN:=1