[Bug other/82704] GCC fails to download prerequisites on busybox distro (unrecognized sha512sum --check)

[keno at juliacomputing dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82704

--- Comment #2 from Keno Fischer <keno at juliacomputing dot com> ---
Well, the script has a separate code path for Darwin anyway, since Darwin's
sha512sum is spelled `shasum -a 512`, but `shasum` also supports `-c` (as well
as `--check`).