xbmk: don't call mkdir. use xbmkdir (new function)

xbmkdir checks if a directory exists, before running
mkdir, and then still uses -p

i was testing xbmk on arch linux today, and noticed
that it errored out when a directory already exists.

i'm mitigating against buggy or differently behaving
mkdir implementations this way, by wrapping around
it.

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

include/lib.sh

@@ -8,12 +8,6 @@
 cbfstool="elf/coreboot/default/cbfstool"
 rmodtool="elf/coreboot/default/rmodtool"
 
-remkdir()
-{
-	x_ rm -Rf "$@"
-	x_ mkdir -p "$@"
-}
-
 mkrom_tarball()
 {
 	update_xbmkver "$1"
@@ -58,7 +52,7 @@ mktarball()
 	printf "Creating tar archive '%s' from directory '%s'\n" "$2" "$1"
 
 	if [ "${2%/*}" != "$2" ]; then
-		x_ mkdir -p "${2%/*}"
+		x_ xbmkdir "${2%/*}"
 	fi
 
 	x_ tar -c "$1" | xz -T$XBMK_THREADS -9e > "$2" || \
@@ -169,6 +163,24 @@ build_sbase()
 	fi
 }
 
+remkdir()
+{
+	x_ rm -Rf "$@"
+	x_ xbmkdir "$@"
+}
+
+xbmkdir()
+{
+	while [ $# -gt 0 ]
+	do
+		if [ ! -d "$1" ]; then
+			x_ mkdir -p "$1"
+		fi
+
+		shift 1
+	done
+}
+
 fx_()
 {
 	xchk fx_ "$@"