build: Fix AUTHORS generation

build: Fix AUTHORS generation

Using s/#authorslist#/$$out/ makes perl eat @domain part of all email
addresses from $out since it tries to interpret them as array variables.
I'm not sure if we can escape those in s/// but I know we can use print:

    s/#authorslist#// and print '$$out'

to tell perl not to even look inside $out.

This patch also fixes gen-AUTHORS so that it works in VPATH.