Build issue with guile 2.0.14

[W. J. van der Laan]

Configure by default passes "-O1" to guild, causing a compile error here with 
guile 2.0.14:

> /usr/bin/guild compile -O1 -L /data/src/mes/module -L /data/src/mes/build-aux 
> -L /data/src/mes/scripts -o module/mes/getopt-long.go 
> /data/src/mes/module/mes/getopt-long.scm
>
> 1: unrecognized option

It comes from the following expression:

>            (guild-optimize (let ((guile-version (and=> (find-dep "guile" 
> deps) dependency-version-found)))
>                             (and guile-version (tuple< '(2) guile-version) 
> "-O1")))

I don't know what the rationale for it is so can't propose a fix. I worked 
around it by replacing it with just "-O" which appears to work here.

W.