fix macOS build

Summary: Darwin libc doesn't implement quick_exit, so use std::_Exit instead.

Reviewed By: yfeldblum

Differential Revision: D23592838

fbshipit-source-id: bda318216239965e14b4c97ca184a2303353ed73

folly/synchronization/test/SmallLocksTest.cpp

@@ -19,6 +19,7 @@
 #include <cassert>
 #include <condition_variable>
 #include <cstdio>
+#include <cstdlib>
 #include <mutex>
 #include <string>
 #include <thread>
@@ -208,7 +209,7 @@ TEST(SmallLocks, PicoSpinLockThreadSanitizer) {
             std::lock_guard<Lock> ga(a);
             // If halt_on_error is turned off for TSAN, then death would
             // happen on exit, so give that a chance as well.
-            std::quick_exit(1);
+            std::_Exit(1);
           }(),
           "Cycle in lock order graph");
     }
@@ -440,7 +441,7 @@ TEST(SmallLocksk, MicroSpinLockThreadSanitizer) {
             std::lock_guard<MicroSpinLock> ga(a);
             // If halt_on_error is turned off for TSAN, then death would
             // happen on exit, so give that a chance as well.
-            std::quick_exit(1);
+            std::_Exit(1);
           }(),
           "Cycle in lock order graph");
     }
@@ -464,7 +465,7 @@ TEST(SmallLocksk, MicroSpinLockThreadSanitizer) {
                 *reinterpret_cast<MicroSpinLock*>(&a));
             // If halt_on_error is turned off for TSAN, then death would
             // happen on exit, so give that a chance as well.
-            std::quick_exit(1);
+            std::_Exit(1);
           }(),
           "Cycle in lock order graph");
     }