./mtr --skip-not-found

New mtr option --skip-not-found makes it to show not found tests
as skipped

main.a                                   [ skipped ]  not found

(but only if the test was specified with the suite name)
and not error out early with

mysql-test-run: *** ERROR: Could not find 'a' in 'main' suite

This is useful in buildbot, on builders that generate the list
of tests dynamically.

mysql-test/lib/mtr_cases.pm

@@ -154,6 +154,16 @@ sub collect_test_cases ($$$$) {
         {
 	  push (@$cases, @this_case);
 	}
+	elsif ($::opt_skip_not_found)
+        {
+          push @$cases, My::Test->new
+            (
+             name          => "$sname.$tname",
+             shortname     => $tname,
+             skip          => 1,
+             comment       => 'not found',
+            );
+        }
         else
 	{
 	  mtr_error("Could not find '$tname' in '$sname' suite");

mysql-test/mysql-test-run.pl

@@ -259,6 +259,7 @@ sub using_extern { return (keys %opts_extern > 0);};
 
 our $opt_fast= 0;
 our $opt_force= 0;
+our $opt_skip_not_found= 0;
 our $opt_mem= $ENV{'MTR_MEM'};
 our $opt_clean_vardir= $ENV{'MTR_CLEAN_VARDIR'};
 
@@ -1158,6 +1159,7 @@ sub command_line_setup {
 
              # Control what test suites or cases to run
              'force+'                   => \$opt_force,
+             'skip-not-found'           => \$opt_skip_not_found,
              'suite|suites=s'           => \$opt_suites,
              'skip-rpl'                 => \&collect_option,
              'skip-test=s'              => \&collect_option,
@@ -5802,6 +5804,8 @@ Options to control what test suites or cases to run
                         the execution will continue from the next test file.
                         When specified twice, execution will continue executing
                         the failed test file from the next command.
+  skip-not-found        It is not an error if a test was not found in a
+                        specified test suite. Test will be marked as skipped.
   do-test=PREFIX or REGEX
                         Run test cases which name are prefixed with PREFIX
                         or fulfills REGEX