Fix dotest.py '-p' option for multi-process mode

Summary:
The '-p' option for dotest.py was ignored in multiprocess mode,
as the -p argument to the inferior would overwrite the -p argument
passed on the command line.

Reviewers: zturner, tfiala

Subscribers: lldb-commits, sas

Differential Revision: http://reviews.llvm.org/D18779

Change by Francis Ricci <fjricci@fb.com>

This is a cherry-pick of r265422

llvm-svn: 270129

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

@@ -420,6 +420,10 @@ def process_dir(root, files, dotest_argv, inferior_pid_events):
     results = []
     for (base_name, full_test_path) in files:
         import __main__ as main
+        global dotest_options
+        if dotest_options.p and not re.search(dotest_options.p, base_name):
+            continue
+
         script_file = main.__file__
         command = ([sys.executable, script_file] +
                    dotest_argv +