setup-HOL4: prefer closest HOL4 directory

Also do not rely on `ls` sort order.

Signed-off-by: Matthew Brecknell <Matthew.Brecknell@data61.csiro.au>

convert license headers to SPDX

Better output from HOL4 setup script.

Restore some functionality for quoting failure details.

Edit typo in script.

New directory of scripts.

In particular, move some setup code for making sure HOL4 is running
from seL4-example/configure_default.sh into its own script.

Also copy in a debug script, which I've had privately for a long
while now. It's a collection of snippets which are useful to quote
to the interactive python interpreter to diagnose various failures.