Automatic merge from submit-queue

Prefer sha1sum (C) to shasum (Perl).

This should avoid spamming build-log.txt with messages like:

    perl: warning: Setting locale failed.
    perl: warning: Please check that your locale settings:
        LANGUAGE = (unset),
        LC_ALL = (unset),
        LANG = "en_US.UTF-8"
        are supported and installed on your system.
    perl: warning: Falling back to the standard locale ("C").

OSX has shasum but not sha1sum, which is part of GNU coreutils.