Clears CLOEXEC flag on descriptor
Clones descriptor, returning a new SafeDescriptor that refers to the same file
descriptor. The cloned descriptor will have the FD_CLOEXEC flag set but will not share any
other file descriptor flags with descriptor.
Clones fd, returning a new file descriptor that refers to the same open file as fd. The
cloned fd will have the FD_CLOEXEC flag set but will not share any other file descriptor
flags with fd.
Apply the specified modification to the file descriptor’s flags.
Adds CLOEXEC flag on descriptor