I m attaching a patch that lets you build taxbird with --as-needed.
Please remove the filtering of the flag as it's not really a good idea to filter it at all. If you can't fix it right away just send me an email next time and I'll see to look at it ;)
[Yes I know what guile report is LDFLAGS as per bug #202205, but that's a bug of it, and it should not break anything to leave it that way for now]
Created attachment 155861 [details, diff]
You can replace flag-o-matic inherit with autotools, and then apply this patch and call eautoreconf in src_unpack, that will be enough.
You can also remove src_compile as it's the default.
Committed this since I had it applied locally and wanted to remove the filtering.