folly: get building with gcc-4.7.1

Summary:
A lot of libstdc++-4.7 headers dropped includes of unistdc.h, so
we'll probably see more of these.

Test Plan: built folly

Reviewed By: simpkins@fb.com

FB internal diff: D508871

diff --git a/folly/experimental/EventCount.h b/folly/experimental/EventCount.h
index df1486486f8f1a6676a8701c3eb19dd2d9bede09..3316fbf91ac2c8a28d03454a18a4153e78afa4d1 100644 (file)
--- a/folly/experimental/EventCount.h
+++ b/folly/experimental/EventCount.h
@@ -17,6 +17,7 @@
 #ifndef FOLLY_EXPERIMENTAL_EVENTCOUNT_H_
 #define FOLLY_EXPERIMENTAL_EVENTCOUNT_H_
 
+#include <unistd.h>
 #include <syscall.h>
 #include <linux/futex.h>
 #include <sys/time.h>