Add <error.h>.

Bug: https://code.google.com/p/android/issues/detail?id=79170
Change-Id: Id91765fac45124545e2674a5b2c814707c1a448b
diff --git a/libc/Android.mk b/libc/Android.mk
index 71ddbd3..522d514 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -112,6 +112,7 @@
     bionic/epoll_pwait.cpp \
     bionic/epoll_wait.cpp \
     bionic/__errno.cpp \
+    bionic/error.cpp \
     bionic/eventfd_read.cpp \
     bionic/eventfd_write.cpp \
     bionic/ffs.cpp \