openvswitch: openvswitch.mk: add ovs_common_depends variable

This is to address the need that openvswitch starting with 2.13 now
depends on libunwind for handling SIGSEGV (upstream commit e2ed6fbeb18
("fatal-signal: Catch SIGSEGV and print backtrace"))

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

net/openvswitch/Makefile

@@ -17,7 +17,7 @@ include ./openvswitch.mk
 #
 PKG_NAME:=openvswitch
 PKG_VERSION:=$(ovs_version)
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://www.openvswitch.org/releases/
 PKG_HASH:=dd5f727427e36cab22bdeae61529d8c8fccacc53d968cfa7658f7f935ddda531
@@ -155,6 +155,8 @@ ovs_kmod_openvswitch-lisp-intree_depends:= +kmod-openvswitch-intree
 ovs_kmod_openvswitch-lisp-intree_files:= $(ovs_kmod_intree_dir)/vport-lisp.ko
 $(eval $(call OvsKmodPackageTemplate,openvswitch-lisp-intree))
 
+ovs_common_depends:= +libatomic +libunbound +libunwind
+
 # Dependency review
 #
 #	for f in sbin/*;   do echo $f; readelf -d $f | grep -i shared; done