Use <condition_variable> and <mutex.h> from MinGW

New MinGW prebuilts update includes pthreads and C++11 threads support.
Use mutex.h and condition_variable provided by MinGW.

Test: Build AOSP with new MinGW prebuilts
Change-Id: Ia8f890f86652612df3fc2618c2bfbb450a5a2f52
diff --git a/sysdeps_test.cpp b/sysdeps_test.cpp
index 740f283..f871675 100644
--- a/sysdeps_test.cpp
+++ b/sysdeps_test.cpp
@@ -17,11 +17,10 @@
 #include <gtest/gtest.h>
 #include <unistd.h>
 #include <atomic>
+#include <condition_variable>
 
 #include "adb_io.h"
 #include "sysdeps.h"
-#include "sysdeps/condition_variable.h"
-#include "sysdeps/mutex.h"
 
 static void increment_atomic_int(void* c) {
     sleep(1);