Implement pthread spin.

In order to run tsan unit tests, we need to support pthread spin APIs.

Bug: 18623621
Bug: 25392375
Change-Id: Icbb4a74e72e467824b3715982a01600031868e29
diff --git a/libc/Android.mk b/libc/Android.mk
index 2849591..99a841a 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -584,6 +584,7 @@
     bionic/pthread_setname_np.cpp \
     bionic/pthread_setschedparam.cpp \
     bionic/pthread_sigmask.cpp \
+    bionic/pthread_spinlock.cpp \
 
 libc_thread_atexit_impl_src_files := \
     bionic/__cxa_thread_atexit_impl.cpp \