On e.g. FreeBSD, Bash lives at /usr/local/bin/bash. This change
makes the script find Bash wherever it may be hiding.
Signed-off-by: Gerwin Klein <gerwin.klein@data61.csiro.au>
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.
