Trap in autogen-5.18.16 in interactive mode (#386)

[Googulator]

With the -i option from #386, autogen-5.18.16 hits a trap in bootstrap_autogen. In non-interactive mode, we somehow don't fail here, as if the relevant script was running without -e,

[Googulator]

Tracked down to https://github.com/schierlm/gnu-autogen-bootstrapping/pull/14 - getGuileVersion is missing a return statement, leaving garbage in the return code register, which triggers the ERR trap.