how to set timeout / signal

[Thien-Thi Nguyen]

GNU RCS is failing via timeout (3600 seconds):

  http://hydra.nixos.org/build/1658987

(I  see 3600 in the Information section, and the
duration of 1h 1m 4s seems to corroborate that.)

Is there something i can add to rcs/release.nix to decrease that
value to something like 300 seconds?  Also, IWBN to be able to
configure a signal to send prior to the (presumed) SIGKILL.