libpacketmark: fix call of initialization function

Rather than using the internal symbol _init, simply let the compiler handle
it by marking it as a constructor. This fixes running the initialization on
some architectures like ARM.

libs/libpacketmark/Makefile

@@ -1,9 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libpacketmark
-PKG_VERSION:=1
-
-PKG_BUILD_DIR := $(BUILD_DIR)/$(PKG_NAME)
+PKG_VERSION:=2
 
 include $(INCLUDE_DIR)/package.mk
 

libs/libpacketmark/src/libpacketmark.c

@@ -38,7 +38,8 @@ static int mark;
 static int (*socket_real)(int domain, int type, int protocol);
 
 
-void _init(void) {
+__attribute__((constructor))
+static void init(void) {
 	const char *str = getenv("LIBPACKETMARK_MARK");
 	if (str)
 		mark = atoi(str);