mkisoimages.sh: Avoid creating temporary files in the current directory

Currently the current directory is the parent of the rootfs directory,
but this will change in order to support NO_ROOT builds that use a
metalog manifest, since those need to have the current directory be the
rootfs itself in order for the relative paths to be correct, and we do
not want the non-METALOG case (which passes the directory to makefs) to
pick up leftover temporary .img files from a previous failed build.

Reviewed by:	brooks, emaste, gjb
Differential Revision:	https://reviews.freebsd.org/D33998

release/amd64/mkisoimages.sh

@@ -85,15 +85,16 @@ if [ "$bootable" != "" ]; then
 	done
 
 	# Create a GPT image containing the partitions we need for hybrid boot.
+	hybridfilename=$(mktemp /tmp/hybrid.img.XXXXXX)
 	imgsize=`stat -f %z "$NAME"`
 	$MKIMG -s gpt \
 	    --capacity $imgsize \
 	    -b "$BASEBITSDIR/boot/pmbr" \
 	    -p freebsd-boot:="$BASEBITSDIR/boot/isoboot" \
 	    $espparam \
-	    -o hybrid.img
+	    -o $hybridfilename
 
 	# Drop the PMBR, GPT, and boot code into the System Area of the ISO.
-	dd if=hybrid.img of="$NAME" bs=32k count=1 conv=notrunc
-	rm -f hybrid.img
+	dd if=$hybridfilename of="$NAME" bs=32k count=1 conv=notrunc
+	rm -f $hybridfilename
 fi

release/arm64/mkisoimages.sh

@@ -81,13 +81,14 @@ if [ "$bootable" != "" ]; then
 	done
 
 	# Create a GPT image containing the EFI partition.
+	efifilename=$(mktemp /tmp/efi.img.XXXXXX)
 	imgsize=`stat -f %z "$NAME"`
 	$MKIMG -s gpt \
 	    --capacity $imgsize \
 	    $espparam \
-	    -o efi.img
+	    -o $efifilename
 
 	# Drop the GPT into the System Area of the ISO.
-	dd if=efi.img of="$NAME" bs=32k count=1 conv=notrunc
-	rm -f efi.img
+	dd if=$efifilename of="$NAME" bs=32k count=1 conv=notrunc
+	rm -f $efifilename
 fi

release/riscv/mkisoimages.sh

@@ -81,13 +81,14 @@ if [ "$bootable" != "" ]; then
 	done
 
 	# Create a GPT image containing the EFI partition.
+	efifilename=$(mktemp /tmp/efi.img.XXXXXX)
 	imgsize=`stat -f %z "$NAME"`
 	$MKIMG -s gpt \
 	    --capacity $imgsize \
 	    $espparam \
-	    -o efi.img
+	    -o $efifilename
 
 	# Drop the GPT into the System Area of the ISO.
-	dd if=efi.img of="$NAME" bs=32k count=1 conv=notrunc
-	rm -f efi.img
+	dd if=$efifilename of="$NAME" bs=32k count=1 conv=notrunc
+	rm -f $efifilename
 fi