MDEV-20787 Script dgcov.pl does not work

Author: Anel Husakovic <anel@mariadb.org>

mysql-test/dgcov.pl

@@ -161,8 +161,13 @@ sub gcov_one_file {
     system($cmd)==0 or die "system($cmd): $? $!";
   }
 
-  # now, read the generated file
-  open FH, '<', "$_.gcov" or die "open(<$_.gcov): $!";
+  (my $filename = $_)=~ s/\.[^.]+$//; # remove extension
+  my $gcov_file_path= $File::Find::dir."/$filename.gcov";
+  if (! -f $gcov_file_path)
+  {
+    return;
+  }
+  open FH, '<', "$gcov_file_path" or die "open(<$gcov_file_path): $!";
   my $fname;
   while (<FH>) {
     chomp;