liblog: add unistd.h to vndk log/log.h

Too many vendors assume that this is included, and it's not worth the
effort to clean up.

Bug: 165825252
Test: build
Change-Id: I42fb32be7e5e3201dfc5c58734e3ef5b9251faf1
diff --git a/liblog/include_vndk/log/log.h b/liblog/include_vndk/log/log.h
index ab4adc4..c305661 100644
--- a/liblog/include_vndk/log/log.h
+++ b/liblog/include_vndk/log/log.h
@@ -3,8 +3,9 @@
 #ifndef _LIBS_LOG_LOG_H
 #define _LIBS_LOG_LOG_H
 
-/* Historically vendors have depended on this header being included. */
+/* Historically vendors have depended on these headers being included. */
 #include <fcntl.h>
+#include <unistd.h>
 
 #include <android/log.h>
 #include <log/log_id.h>