don't use build.list to detect multi-tree projects

instead, check for the presence of target.cfg files
not in config/project/ but config/project/tree/

the way this check is done, it merely returns 1 if
config/project/*/target.cfg is detected, and returns
0 in all other cases, even if config/project/target.cfg
exists

that way, if the maintainer accidentally adds a
target.cfg in the main directory, the given multi-tree
project will not break

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

include/lib.sh

@@ -228,3 +228,13 @@ e()
 	eval "$estr"
 	printf "%s %s\n" "$1" "$es2" 1>&2
 }
+
+# return 0 if project is single-tree, otherwise 1
+# e.g. coreboot is multi-tree, so 1
+singletree()
+{
+	for pdir in "config/${1}/"*/target.cfg; do
+		[ ! -e "$pdir" ] && continue
+		[ -f "$pdir" ] && return 1
+	done
+}