Add check for spaces in board and variant names.

bin/cros_overlay_list

Index: bin/cros_overlay_list
diff --git a/bin/cros_overlay_list b/bin/cros_overlay_list
index 1d768663e922cab082796f51466a27da862ad618..1867da25a6761231fa4c09306f57dc1d0b31ebf4 100755
--- a/bin/cros_overlay_list
+++ b/bin/cros_overlay_list
@@ -30,13 +30,13 @@ if [ -z "$FLAGS_board" ] ; then
   exit 1
 fi
 
-if [[ "$FLAGS_board" =~ "_" ]] ; then
-  error "--board name must not contain an underscore (_)."
+if [[ $FLAGS_board =~ [_\ ] ]] ; then
+  error "--board name must not contain an underscore (_) or a space ( )."
   exit 1
 fi
 
-if [[ "$FLAGS_variant" =~ "_" ]] ; then
-  error "--variant name must not contain an underscore (_)."
+if [[ $FLAGS_variant =~ [_\ ] ]] ; then
+  error "--variant name must not contain an underscore (_) or a space ( )."
   exit 1
 fi