dnsmasq: add build option for dnssec

I wasn't sure if this should be default enabled or not and left it disabled.

srcpkgs/dnsmasq/template

@@ -3,7 +3,7 @@ pkgname=dnsmasq
 version=2.78
 revision=1
 hostmakedepends="pkg-config"
-makedepends="dbus-devel libcap-devel libidn-devel"
+makedepends="dbus-devel libcap-devel libidn-devel $(vopt_if dnssec nettle-devel)"
 conf_files="/etc/dnsmasq.conf"
 system_accounts="dnsmasq"
 dnsmasq_homedir="/var/chroot"
@@ -14,8 +14,14 @@ homepage="http://www.thekelleys.org.uk/dnsmasq/doc.html"
 distfiles="http://www.thekelleys.org.uk/${pkgname}/${pkgname}-${version}.tar.gz"
 checksum=c92e5d78aa6353354d02aabf74590d08980bb1385d8a00b80ef9bc80430aa1dc
 
+build_options="dnssec"
+desc_option_dnssec="Enable DNSSEC support via nettle"
+
 do_build() {
 	echo '#define HAVE_DBUS' >> src/config.h
+	if [ "$build_option_dnssec" ]; then
+		echo '#define HAVE_DNSSEC' >> src/config.h
+	fi
 	make CC=$CC CFLAGS="$CFLAGS" LDFLAGS="$LDFLAGS" ${makejobs}
 }
 do_install() {