mkimage-arch: unify usage of brackets around variables

Docker-DCO-1.1-Signed-off-by: Bartłomiej Piotrowski <b@bpiotrowski.pl> (github: Barthalion)

contrib/mkimage-arch.sh

@@ -18,7 +18,7 @@ EXPECT=$(hash expect &>/dev/null)
 
 ROOTFS=$(mktemp -d /tmp/rootfs-archlinux-XXXXXXXXXX)
 
-#packages to ignore for space savings
+# packages to ignore for space savings
 PKGIGNORE=linux,jfsutils,lvm2,cryptsetup,groff,man-db,man-pages,mdadm,pciutils,pcmciautils,reiserfsprogs,s-nail,xfsprogs
  
 expect <<EOF
@@ -46,21 +46,21 @@ arch-chroot $ROOTFS locale-gen
 arch-chroot $ROOTFS /bin/sh -c 'echo "Server = http://mirrors.kernel.org/archlinux/\$repo/os/\$arch" > /etc/pacman.d/mirrorlist'
 
 # udev doesn't work in containers, rebuild /dev
-DEV=${ROOTFS}/dev
-rm -rf ${DEV}
-mkdir -p ${DEV}
-mknod -m 666 ${DEV}/null c 1 3
-mknod -m 666 ${DEV}/zero c 1 5
-mknod -m 666 ${DEV}/random c 1 8
-mknod -m 666 ${DEV}/urandom c 1 9
-mkdir -m 755 ${DEV}/pts
-mkdir -m 1777 ${DEV}/shm
-mknod -m 666 ${DEV}/tty c 5 0
-mknod -m 600 ${DEV}/console c 5 1
-mknod -m 666 ${DEV}/tty0 c 4 0
-mknod -m 666 ${DEV}/full c 1 7
-mknod -m 600 ${DEV}/initctl p
-mknod -m 666 ${DEV}/ptmx c 5 2
+DEV=$ROOTFS/dev
+rm -rf $DEV
+mkdir -p $DEV
+mknod -m 666 $DEV/null c 1 3
+mknod -m 666 $DEV/zero c 1 5
+mknod -m 666 $DEV/random c 1 8
+mknod -m 666 $DEV/urandom c 1 9
+mkdir -m 755 $DEV/pts
+mkdir -m 1777 $DEV/shm
+mknod -m 666 $DEV/tty c 5 0
+mknod -m 600 $DEV/console c 5 1
+mknod -m 666 $DEV/tty0 c 4 0
+mknod -m 666 $DEV/full c 1 7
+mknod -m 600 $DEV/initctl p
+mknod -m 666 $DEV/ptmx c 5 2
 
 tar --numeric-owner -C $ROOTFS -c . | docker import - archlinux
 docker run -i -t archlinux echo Success.