xen: do not install any symlink in /boot for the hypervisor.

... otherwise if /boot is fat, the extraction will fail with EPERM because
fat filesystem does not support links.

Reported by mlen@irc.

srcpkgs/xen/template

@@ -1,7 +1,7 @@
 # Template file for 'xen'
 pkgname=xen
 version=4.5.1
-revision=1
+revision=2
 wrksrc="xen-${version}"
 short_desc="The Xen hypervisor utilities"
 maintainer="Juan RP <xtraeme@voidlinux.eu>"
@@ -91,6 +91,8 @@ do_install() {
 	vsv xen
 	vsv xenconsoled
 	vsv xenstored
+
+	rm -f ${DESTDIR}/boot/xen-${version%.*}.gz
 }
 
 xen-hypervisor_package() {