lbmk: don't handle TMPDIR directly

lbmk creates TMPDIR as /tmp/xbmk_*, but it's theoretically
possible that something could re-export it by mistake.

this change retains the same initialisation, but further
use is now via a new variable "xbmktmp", that stores the
value of TMPDIR upon lbmk's initialisation of it.

this reduces the chance of such a bug in the future, as
described above, so it is a preemptive/preventative fix.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/lib.sh

@@ -50,7 +50,7 @@ chkvars()
 }
 
 eval "`setvars "" _nogit board reinstall versiondate aur_notice configdir \
-    datadir version relname`"
+    datadir version relname xbmktmp`"
 
 for fv in version versiondate; do
 	eval "[ ! -f \".$fv\" ] || read -r $fv < \".$fv\" || :"
@@ -127,6 +127,7 @@ if [ -z "${TMPDIR+x}" ]; then
 	[ -f "lock" ] && $err "$xbmkpwd/lock exists. Is a build running?"
 	export TMPDIR="/tmp"
 	export TMPDIR="$(mktemp -d -t xbmk_XXXXXXXX)"
+	xbmktmp="$TMPDIR"
 	touch lock || $err "cannot create 'lock' file"
 	x_ rm -Rf "$XBMK_CACHE/xbmkpath" "$XBMK_CACHE/gnupath"
 	x_ mkdir -p "$XBMK_CACHE/gnupath" "$XBMK_CACHE/xbmkpath"
@@ -144,6 +145,7 @@ if [ -z "${TMPDIR+x}" ]; then
 	rm -f lock || xbmk_rval=1
 	exit $xbmk_rval
 fi
+xbmktmp="$TMPDIR"
 
 # if "y": a coreboot target won't be built if target.cfg says release="n"
 # (this is used to exclude certain build targets from releases)

include/rom.sh

@@ -12,7 +12,8 @@ mkserprog()
 
 	[ "$1" = "pico" ] && mkpicotool
 
-	basename -as .h "$serdir/"*.h > "$TMPDIR/ser" || $err "!mk $1 $TMPDIR"
+	basename -as .h "$serdir/"*.h > "$xbmktmp/ser" || \
+	    $err "!mk $1 $xbmktmp"
 
 	while read -r sertarget; do
 		[ "$1" = "pico" ] &&
@@ -31,7 +32,7 @@ mkserprog()
 		    "$sersrc" BOARD=$sertarget
 		x_ mkdir -p "bin/serprog_$1"
 		x_ mv "$serx" "bin/serprog_$1/serprog_$sertarget.${serx##*.}"
-	done < "$TMPDIR/ser"
+	done < "$xbmktmp/ser"
 
 	[ "$XBMK_RELEASE" = "y" ] && mkrom_tarball "bin/serprog_$1"; :
 }
@@ -115,7 +116,7 @@ mkcorebootbin()
 {
 	[ "$target" = "$tree" ] && return 0
 
-	tmprom="$TMPDIR/coreboot.rom"
+	tmprom="$xbmktmp/coreboot.rom"
 	$dry x_ cp "$srcdir/build/coreboot.rom" "$tmprom"
 
 	initmode="${defconfig##*/}"
@@ -201,8 +202,8 @@ add_grub()
 	    _grubname="fallback/payload"
 	cbfs "$tmprom" "$grubelf" "$_grubname"
 	printf "set grub_scan_disk=\"%s\"\n" "$grub_scan_disk" \
-	    > "$TMPDIR/tmpcfg" || $err "$target: !insert scandisk"
-	cbfs "$tmprom" "$TMPDIR/tmpcfg" scan.cfg raw
+	    > "$xbmktmp/tmpcfg" || $err "$target: !insert scandisk"
+	cbfs "$tmprom" "$xbmktmp/tmpcfg" scan.cfg raw
 	[ "$initmode" != "normal" ] && [ "$displaymode" != "txtmode" ] && \
 	    cbfs "$tmprom" "$grubdata/background/background1280x800.png" \
 	    "background.png" raw; :

include/vendor.sh

@@ -48,11 +48,11 @@ vendor_download()
 
 readkconfig()
 {
-	x_ rm -f "$TMPDIR/cbcfg"
+	x_ rm -f "$xbmktmp/cbcfg"
 	cbcfg="`check_defconfig "$boarddir"`" || for cbc in $cv; do
-		grep "$cbc" "$cbcfg" 1>>"$TMPDIR/cbcfg" 2>/dev/null || :
+		grep "$cbc" "$cbcfg" 1>>"$xbmktmp/cbcfg" 2>/dev/null || :
 	done
-	eval "`setcfg "$TMPDIR/cbcfg" 1`"
+	eval "`setcfg "$xbmktmp/cbcfg" 1`"
 
 	for c in $cvchk; do
 		eval "[ \"\${$c}\" = \"/dev/null\" ] && continue"