Explicitly import subprocess

For some reason on one of our bots subprocess wasn't already
imported. Do so explicitly.

llvm-svn: 328715

lldb/packages/Python/lldbsuite/test/lang/cpp/trivial_abi/TestTrivialABI.py

@@ -9,6 +9,7 @@ import os
 import time
 import re
 import lldb
+import subprocess
 import lldbsuite.test.lldbutil as lldbutil
 from lldbsuite.test.lldbtest import *
 from lldbsuite.test import decorators