libartnet: Fix compilation with GCC8

Previous GCC7 fix was incorrect and GCC8 correctly complains about it.
Fix it properly.

Also cleaned up the Makefile for consistency between packages.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
(cherry-picked from fac6f0e0a5)

libs/libartnet/Makefile

@@ -9,24 +9,25 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libartnet
 PKG_VERSION:=1.1.2
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://github.com/OpenLightingProject/libartnet/releases/download/1.1.2
 PKG_HASH:=19cdda434e208a81ddd138377f11046364438e40e34542ae101d6aa3fcaec696
 
 PKG_MAINTAINER:=Martijn Zilverschoon <martijn@friedzombie.com>
-
 PKG_LICENSE:=GPL-2.1
 PKG_LICENSE_FILES:=COPYING
 
+PKG_INSTALL:=1
+
 include $(INCLUDE_DIR)/package.mk
 
 define Package/libartnet
 	SECTION:=libs
 	CATEGORY:=Libraries
 	TITLE:=Libartnet is an implementation of the ArtNet protocol.
-	URL:=http://www.openlighting.org/libartnet-main/
+	URL:=https://www.openlighting.org/libartnet-main/
 endef
 
 define Package/libartnet/description
@@ -34,16 +35,6 @@ define Package/libartnet/description
 	transmission of DMX and related data over IP networks.
 endef
 
-define Build/Configure
-	$(call Build/Configure/Default)
-endef
-
-define Build/Compile
-	$(MAKE) -C $(PKG_BUILD_DIR) \
-	DESTDIR="$(PKG_INSTALL_DIR)" \
-	all install
-endef
-
 define Build/InstallDev
 	mkdir -p $(1)/usr/include
 	$(CP) $(PKG_INSTALL_DIR)/usr/include/artnet $(1)/usr/include/