xbmk: remove even more eval statements

in one or two cases, the use of eval is retained, but
modified so as to be safer.

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

include/lib.sh

@@ -91,7 +91,6 @@ setvars()
 	_setvars=""
 
 	if [ $# -lt 2 ]; then
-		printf "err \"setvars: too few args\\n\""
 
 		return 0
 	else
@@ -107,14 +106,6 @@ setvars()
 	fi
 }
 
-chkvars()
-{
-	while [ $# -gt 0 ]; do
-		eval "[ -n \"\${$1+x}\" ] || err \"$1 unset\""
-		eval "[ -n \"\$$1\" ] || err \"$1 unset\"; shift 1; :"
-	done; :
-}
-
 # return 0 if project is single-tree, otherwise 1
 # e.g. coreboot is multi-tree, so 1
 singletree()