With the introduction of the ubus notifications, we would now fail building dnsmasq with external toolchains that don't automatically search for headers. Pass TARGET_CPPFLAGS to the Makefile to resolve that. Fixes:34a206bc11("dnsmasq: add ubus notifications for new leases") Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> (cherry picked from commitef485bb23d)