lua: use target LDFLAGS

This adds '-static' to the link command when BR2_STATIC_LIBS=y, making the lua
binary really static.

Cc: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Acked-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/lua/lua.mk

@@ -70,6 +70,7 @@ define LUA_BUILD_CMDS
 	CC="$(TARGET_CC)" RANLIB="$(TARGET_RANLIB)" \
 	CFLAGS="$(TARGET_CFLAGS) $(LUA_CFLAGS)" \
 	MYLIBS="$(LUA_MYLIBS)" AR="$(TARGET_CROSS)ar rcu" \
+	MYLDFLAGS="$(TARGET_LDFLAGS)" \
 	BUILDMODE=$(LUA_BUILDMODE) \
 	PKG_VERSION=$(LUA_VERSION) -C $(@D)/src all
 endef