mkisoimages.sh: remove obsolete x$var convention

Ancient shells had trouble with empty variables but this has not been
relevant for FreeBSD for a very long time (decades?).

release/amd64/mkisoimages.sh

@@ -23,7 +23,7 @@
 # extra-bits-dir, if provided, contains additional files to be merged
 # into base-bits-dir as part of making the image.
 
-if [ "x$1" = "x-b" ]; then
+if [ "$1" = "-b" ]; then
 	# This is highly x86-centric and will be used directly below.
 	bootable="-o bootimage=i386;$4/boot/cdboot -o no-emul-boot"
 

release/i386/mkisoimages.sh

@@ -23,7 +23,7 @@
 # extra-bits-dir, if provided, contains additional files to be merged
 # into base-bits-dir as part of making the image.
 
-if [ "x$1" = "x-b" ]; then
+if [ "$1" = "-b" ]; then
 	# This is highly x86-centric and will be used directly below.
 	bootable="-o bootimage=i386;$4/boot/cdboot -o no-emul-boot"
 	shift

release/powerpc/mkisoimages.sh

@@ -23,7 +23,7 @@
 # extra-bits-dir, if provided, contains additional files to be merged
 # into base-bits-dir as part of making the image.
 
-if [ "x$1" = "x-b" ]; then
+if [ "$1" = "-b" ]; then
 	# Apple boot code
 	uudecode -o /tmp/hfs-boot-block.bz2 "`dirname "$0"`/hfs-boot.bz2.uu"
 	bzip2 -d /tmp/hfs-boot-block.bz2

release/sparc64/mkisoimages.sh

@@ -40,7 +40,7 @@ echo "/dev/iso9660/$LABEL / cd9660 ro 0 0" > "$BASEBITSDIR/etc/fstab"
 makefs -t cd9660 -o rockridge -o label="$LABEL" -o publisher="$publisher" "$NAME.tmp" "$@"
 rm -f "$BASEBITSDIR/etc/fstab"
 
-if [ "x$BOPT" != "x-b" ]; then
+if [ "$BOPT" != "-b" ]; then
 	mv "$NAME.tmp" "$NAME"
 	exit 0
 fi