perl-cross tree has both Configure and configure, which causes
checkcase.t to fail. Skip them.

--- a/t/porting/checkcase.t
+++ b/t/porting/checkcase.t
@@ -25,6 +25,8 @@
 
 	   # Special exemption for Makefile, makefile
 	   return if $name =~ m!\A[Mm]akefile\z!;
+	   # same for Configure, configure in perl-cross
+	   return if $name =~ m!\A[Cc]onfigure\z!;
 
 	   if ($name eq '.git') {
 	       # Don't scan the .git directory, as its contents are outside