Ensure <fcntl.h> defines the S_* constants from <sys/stat.h>.

POSIX says "The <fcntl.h> header shall define the symbolic constants for file
modes for use as values of mode_t as described in <sys/stat.h>".

Needed to build ToT strace.

Change-Id: Ia85a51ef6fd86a48084fe48ce24963000a937d37
Merge "Ensure <fcntl.h> defines the S_* constants from <sys/stat.h>."