This implements GitHub PR #115 on the current repo state. /usr/bin/env
is already used for other (cmake/python/etc) invocations, and this PR
brings bash/sh into line with that for slightly improved portability.
Co-authored-by: Douglas Wilson <douglas.wilson@gmail.com>
Signed-off-by: Gerwin Klein <gerwin.klein@proofcraft.systems>
This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.
