Added native utilities to mount/umount/chroot via capabilities(7).

Three new helpers will now be installed into ${libexecdir}:
 - xbps-src-capchroot needs to have set CAP_SYS_CHROOT ep.
 - xbps-src-chroot-cap{,u}mount: needs to have set CAP_SYS_ADMIN ep.

That means that libcap and setcap(8) are now required to install
xbps-src and use it as normal user.

--HG--
extra : convert_revision : 586d6526079e085f86bf3e393459d429f6f0ef99

xbps-src/libexec/xbps-src-chroot-helper.sh.in

@@ -35,20 +35,26 @@ REQFS="sys proc dev xbps"
 
 mount_chroot_fs()
 {
-	local cnt f blah
+	local cnt f blah dowrite
 
 	for f in ${REQFS}; do
 		if [ ! -f ${XBPS_MASTERDIR}/.${f}_mount_bind_done ]; then
+			unset dowrite
 			echo -n "=> Mounting /${f} in chroot... "
 			if [ ! -d ${XBPS_MASTERDIR}/${f} ]; then
 				mkdir -p ${XBPS_MASTERDIR}/${f}
 			fi
 			case ${f} in
-				xbps) blah=${XBPS_DISTRIBUTIONDIR};;
+				xbps)
+					blah=${XBPS_DISTRIBUTIONDIR}
+					dowrite="-w"
+					;;
 				*) blah=/${f};;
 			esac
 			[ ! -d ${blah} ] && echo "failed." && continue
-			mount --bind ${blah} ${XBPS_MASTERDIR}/${f}
+			@@XBPS_INSTALL_LIBEXECDIR@@/xbps-src-chroot-capmount \
+				${dowrite} ${blah} ${XBPS_MASTERDIR}/${f} \
+				2>/dev/null
 			if [ $? -eq 0 ]; then
 				echo 1 > ${XBPS_MASTERDIR}/.${f}_mount_bind_done
 				echo "done."
@@ -75,7 +81,8 @@ umount_chroot_fs()
 			echo ${cnt} > ${XBPS_MASTERDIR}/.${fs}_mount_bind_done
 		else
 			echo -n "=> Unmounting ${fs} from chroot... "
-			umount -f ${XBPS_MASTERDIR}/${fs}
+			@@XBPS_INSTALL_LIBEXECDIR@@/xbps-src-chroot-capumount \
+				${XBPS_MASTERDIR}/${fs} 2>/dev/null
 			if [ $? -eq 0 ]; then
 				rm -f ${XBPS_MASTERDIR}/.${fs}_mount_bind_done
 				echo "done."