Print the list of failed suites in verbose mode

In verbose mode, the full output of each failing suite is printed out,
which for some suites runs in the 1000s of lines. If you didn't redirect
output to a file, this is a lot to scroll and can make it hard to
quickly identify which test suites failed.

So, let's print out that information at the end. This is useful
information for starting to figure out what went wrong.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/scripts/run-test-suites.pl b/tests/scripts/run-test-suites.pl
index 15fa8bc..22eadd1 100755
--- a/tests/scripts/run-test-suites.pl
+++ b/tests/scripts/run-test-suites.pl
@@ -74,7 +74,7 @@
 
 my $prefix = $^O eq "MSWin32" ? '' : './';
 
-my ($failed_suites, $total_tests_run, $failed, $suite_cases_passed,
+my (@failed_suites, $total_tests_run, $failed, $suite_cases_passed,
     $suite_cases_failed, $suite_cases_skipped, $total_cases_passed,
     $total_cases_failed, $total_cases_skipped );
 my $suites_skipped = 0;
@@ -112,7 +112,7 @@
             pad_print_center( 72, '-', "End $suite" );
         }
     } else {
-        $failed_suites++;
+        push @failed_suites, $suite;
         print "FAIL\n";
         if( $verbose ) {
             pad_print_center( 72, '-', "Begin $suite" );
@@ -139,12 +139,17 @@
 }
 
 print "-" x 72, "\n";
-print $failed_suites ? "FAILED" : "PASSED";
+print @failed_suites ? "FAILED" : "PASSED";
 printf( " (%d suites, %d tests run%s)\n",
         scalar(@suites) - $suites_skipped,
         $total_tests_run,
         $suites_skipped ? ", $suites_skipped suites skipped" : "" );
 
+if( $verbose && @failed_suites ) {
+    # the output can be very long, so provide a summary of which suites failed
+    print "      failed suites : @failed_suites\n";
+}
+
 if( $verbose > 1 ) {
     print "  test cases passed :", $total_cases_passed, "\n";
     print "             failed :", $total_cases_failed, "\n";
@@ -159,5 +164,5 @@
     }
 }
 
-exit( $failed_suites ? 1 : 0 );
+exit( @failed_suites ? 1 : 0 );