Show why clang analyzer could not be executed

[Ramin]

Summary

when an unknown paramater is used when running scan-build

it just prints "could not find clang line"

this patch shows the error message

clang/tools/scan-build/libexec/ccc-analyzer

 
   # Invoke 'system', STDOUT and STDERR are output to a temporary file.
   system $Command, @_;
+  my $ret = $?;
 
   # Restore STDOUT and STDERR.
   open STDOUT, ">&", \*OLDOUT;
   open STDERR, ">&", \*OLDERR;
 
+  if ($ret != 0) {
+    print "failed to run $Command \n";
+    while(<$TmpFH>){
+       print $_;
+    }
+  }
+
   return $TmpFH;
 }