[lldb] Print the command output when 'expect' fails even if a custom msg is passed

Currently if 'expect' fails and a custom msg is supplied, then lldbtest
will not print the actual command output. This makes it impossible to know
why the test actually failed. This just prints the command output even
if the msg parameter was supplied.

lldb/packages/Python/lldbsuite/test/lldbtest.py

@@ -2364,7 +2364,8 @@ FileCheck output:
                     break
 
         self.assertTrue(matched if matching else not matched,
-                        msg if msg else EXP_MSG(str, output, exe))
+                        msg + "\nCommand output:\n" + EXP_MSG(str, output, exe)
+                        if msg else EXP_MSG(str, output, exe))
 
     def expect_expr(
             self,