[SR-1639] Move sourcekitdInProc to std::mutex

SourceKit's in-process mode uses libdispatch sparingly. Removing all usages of
libdispatch would allow SourceKit to more easily be ported to Linux. We can
begin this process with the `sourcekitd-test` executable, which makes use of
`sourcekitd_send_request_sync`.

Migrate this usage to the C++ std::condition_variable.

Author: modocache

tools/SourceKit/tools/sourcekitd/bin/InProc/sourcekitdInProc.cpp

@@ -18,9 +18,9 @@
 #include "llvm/Support/Mutex.h"
 #include "llvm/Support/Path.h"
 
-// FIXME: Portability ?
 #include <Block.h>
-#include <dispatch/dispatch.h>
+#include <condition_variable>
+#include <mutex>
 
 #ifdef LLVM_ON_WIN32
 #include <windows.h>
@@ -102,16 +102,17 @@ void sourcekitd::set_interrupted_connection_handler(
 //===----------------------------------------------------------------------===//
 
 sourcekitd_response_t sourcekitd_send_request_sync(sourcekitd_object_t req) {
-  dispatch_semaphore_t sema = dispatch_semaphore_create(0);
+  sourcekitd_response_t ReturnedResp = nullptr;
+  std::condition_variable handleRequestCondition;
 
-  sourcekitd_response_t ReturnedResp;
   sourcekitd::handleRequest(req, [&](sourcekitd_response_t resp) {
     ReturnedResp = resp;
-    dispatch_semaphore_signal(sema);
+    handleRequestCondition.notify_one();
   });
 
-  dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
-  dispatch_release(sema);
+  std::mutex m;
+  std::unique_lock<std::mutex> lk(m);
+  handleRequestCondition.wait(lk, [&]{ return ReturnedResp != nullptr; });
   return ReturnedResp;
 }