Missed a dependency on pthreads.

Change-Id: I060c9c65b07efe89a308fccf71a1096424a7de39
diff --git a/core/cxx_stl_setup.mk b/core/cxx_stl_setup.mk
index c688088..4f41daa 100644
--- a/core/cxx_stl_setup.mk
+++ b/core/cxx_stl_setup.mk
@@ -35,7 +35,7 @@
     ifdef LOCAL_IS_HOST_MODULE
         my_cppflags += -nostdinc++
         my_ldflags += -nodefaultlibs
-        my_ldlibs += -lc -lm
+        my_ldlibs += -lc -lm -lpthread
     endif
 else ifneq ($(filter $(my_cxx_stl),stlport stlport_static),)
     ifndef LOCAL_IS_HOST_MODULE