Base: Update recvfd() man page after addition of options argument

Base/usr/share/man/man2/recvfd.md

@@ -7,7 +7,7 @@ recvfd - receive a file descriptor from a local socket peer
 ```**c++
 #include <sys/socket.h>
 
-int recvfd(int sockfd);
+int recvfd(int sockfd, int options);
 ```
 
 ## Description
@@ -16,6 +16,10 @@ Receive an open file descriptor from a local socket peer connected via `sockfd`.
 
 File descriptors are sent out-of-band and do not affect the regular data streams.
 
+The *options* argument accepts a bitmask of the following flags:
+
+* `O_CLOEXEC`: The opened fd shall be closed on [`exec`(2)](../man2/exec.md).
+
 ## Return value
 
 If a file descriptor is successfully received, it is returned as a non-negative integer. Otherwise, -1 is returned and `errno` is set to indicate the error.