main/linux-grsec: add gmp-dev as depend for -dev

It is needed for constify plugin to be enabled for 3rd party modules

main/linux-grsec/APKBUILD

@@ -4,7 +4,7 @@ _flavor=grsec
 pkgname=linux-${_flavor}
 pkgver=3.3.8
 _kernver=3.3
-pkgrel=0
+pkgrel=1
 pkgdesc="Linux kernel with grsecurity"
 url=http://grsecurity.net
 depends="mkinitfs linux-firmware"
@@ -100,6 +100,7 @@ dev() {
 	# build a tiny kernel module
 	#
 	pkgdesc="Headers and script for third party modules for grsec kernel"
+	depends="gmp-dev"
 	local dir="$subpkgdir"/usr/src/linux-headers-${_abi_release}
 
 	# first we import config, run prepare to set up for building