checksrc.pl: fix handling .checksrc with CRLF

- When parsing .checksrc chomp the (CR)LF line ending.

Prior to this change on Windows checksrc.pl would not process the
symbols in .checksrc properly, since many git repos in Windows use auto
crlf to check out files with CRLF line endings.

Closes https://github.com/curl/curl/pull/12924

scripts/checksrc.pl

@@ -120,6 +120,7 @@ sub readlocalfile {
     open(my $rcfile, "<", "$dir/.checksrc") or return;
 
     while(<$rcfile>) {
+        $windows_os ? $_ =~ s/\r?\n$// : chomp;
         $i++;
 
         # Lines starting with '#' are considered comments