[DirectoryWatcher] Fix asserts Mac builds

Add a missing semicolon after an assert. Remove the period from the
assert message while I'm here, because we don't usually have those.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@367984 91177308-0d34-0410-b5e6-96231b3b80d8

lib/DirectoryWatcher/mac/DirectoryWatcher-mac.cpp

@@ -210,7 +210,7 @@ llvm::Expected<std::unique_ptr<DirectoryWatcher>> clang::DirectoryWatcher::creat
 
   assert(!Path.empty() && "Path.empty()");
   auto EventStream = createFSEventStream(Path, Receiver, Queue);
-  assert(EventStream && "EventStream expected to be non-null.")
+  assert(EventStream && "EventStream expected to be non-null");
 
   std::unique_ptr<DirectoryWatcher> Result =
       llvm::make_unique<DirectoryWatcherMac>(EventStream, Receiver, Path);