lib.sh: use xprintf in err()

if more than one argument is provided, it is interpreted
as a command, and the command is outputted.

this means that now for example, where you have:

ls -l foo | err "could not list directory"

you could do:

ls -l foo | err "could not list directory" "$@"

this would show all the arguments given to the calling
function that tried to run "ls"

let's say that function was called bar, you might do:

ls -l foo | err "could not list directory" bar "$@"

right now, it's not easy to provide good debug info
where err is used, unless it was called with x_, which
provides the command/arguments that was bugging out.

with this, we now have an easy and readable/maintainable
way to do the same thing everywhere in xbmk.

this will now be done, in a follow-up commit.

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

include/lib.sh

@@ -149,18 +149,33 @@ dx_()
 
 x_()
 {
-	[ $# -lt 1 ] || [ -n "$1" ] || err "Empty first arg: x_ $(xprintf "$@")"
-	[ $# -lt 1 ] || "$@" || err "Unhandled error for: $(xprintf "$@")"; :
+	[ $# -lt 1 ] || [ -n "$1" ] || err "Empty first arg" "$@"
+	[ $# -lt 1 ] || "$@" || err "Unhandled error" "$@"
 }
 
 xchk()
 {
-	[ $# -lt 3 ] && err "$1 needs at least two arguments: $(xprintf "$@")"
+	[ $# -lt 3 ] && err "$1 needs at least two arguments" "$@"
 	if [ -z "$2" ] || [ -z "$3" ]; then
 		err "arguments must not be empty in $1: \"$2\" \"$3\" "
 	fi
 }
 
+err()
+{
+	if [ $# -eq 1 ]; then
+		printf "ERROR %s: %s\n" "$0" "$1" 1>&2 || :
+	elif [ $# -gt 1 ]; then
+		printf "ERROR %s: %s: in command/function with arguments: " \
+		    "$0" "$1" 1>&2
+		shift 1
+		xprintf "$@" 1>&2
+	else
+		printf "ERROR, but no arguments provided to err\n" 1>&2
+	fi
+	exit 1
+}
+
 xprintf()
 {
 	xprintfargs=0
@@ -172,9 +187,3 @@ xprintf()
 	done
 	[ $xprintfargs -gt 0 ] && printf "\n"; :
 }
-
-err()
-{
-	[ $# -lt 1 ] || printf "ERROR %s: %s\n" "$0" "$1" 1>&2 || :
-	exit 1
-}