libmakepkg/util: use parameter transformation when checking variable type

Now that we require bash 4.4 this is "more correct" than analyzing the
output of declare -p to see if it compares favorably with -a.

Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>

scripts/libmakepkg/util/util.sh.in

@@ -42,7 +42,7 @@ is_array() {
 	local v=$1
 	local ret=1
 
-	if [[ $(declare -p "$v") == declare\ -*([[:alnum:]])a*([[:alnum:]])\ * ]]; then
+	if [[ ${!v@a} = *a* ]]; then
 		ret=0
 	fi