Add missing include and function prototype for sched_getaffinity.

Change-Id: I649633c8d074def5d05bd0c8b92fb680d9d11d51
diff --git a/libc/Android.mk b/libc/Android.mk
index 3c387d2..74175ba 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -170,7 +170,6 @@
 	bionic/recv.c \
 	bionic/sched_cpualloc.c \
 	bionic/sched_cpucount.c \
-	bionic/sched_getaffinity.c \
 	bionic/sched_getcpu.c \
 	bionic/semaphore.c \
 	bionic/send.c \
@@ -264,6 +263,7 @@
     bionic/raise.cpp \
     bionic/sbrk.cpp \
     bionic/scandir.cpp \
+    bionic/sched_getaffinity.cpp \
     bionic/__set_errno.cpp \
     bionic/setlocale.cpp \
     bionic/signalfd.cpp \