Include what you use: <unistd.h>

This was transitively included, but no longer is, so it must be
explicitly included.

Exempt-From-Owner-Approval: Janitorial
Test: build
Change-Id: I9c57174e4dcf5dfddb44498d8faa556531894b1e
diff --git a/opengl/libs/EGL/FileBlobCache.cpp b/opengl/libs/EGL/FileBlobCache.cpp
index 96a29e1..3284778 100644
--- a/opengl/libs/EGL/FileBlobCache.cpp
+++ b/opengl/libs/EGL/FileBlobCache.cpp
@@ -21,6 +21,7 @@
 #include <inttypes.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 #include <log/log.h>