check mktemp return value

[Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

in slackware the default mktemp is not from coreutils.
A simply make in test directory mangled my rootfs due
to initdir is blank

Also mktemp could failed with other reason like ENOSPC or EPERM

Signed-off-by: Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 dracut |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/dracut b/dracut
index c9329bd..8237f7a 100755
--- a/dracut
+++ b/dracut
@@ -472,6 +472,10 @@ fi

 readonly TMPDIR=/var/tmp
 readonly initdir=$(mktemp --tmpdir=/var/tmp/ -d -t initramfs.XXXXXX)
+[ -z $initdir ] && {
+    dfatal "mktemp failed."
+    exit 1
+}

 # clean up after ourselves no matter how we die.
 trap 'ret=$?;[[ $keep ]] && echo "Not removing $initdir." >&2 || rm -rf
"$initdir";exit $ret;' EXIT
-- 
1.7.4.4