[OE-core] Preventing RRECOMMENDS from installing

[Anders Darander]

Is there a simple way, in a bbappend-file to prevent packages in an
RRECOMMENDS from being installed? E.g. if package foo has:
RRECOMMENDS_${PN} += "bar"

I'd reluctant to rewrite RRECOMMENDS_${PN} completely, as foo sets
RRECOMMENDS using += (or =+), thus I'd like not to remove other packages
from RRECOMMENDS. 

If possible, I'd like to avoid patching the foo.bb-file, and just have a
foo.bbappend in my own layer.

I've unsuccesfully tried different variants using oe_filter_out, but
they don't seems to prevent bar from being installed.

Thanks in advance for any hints!

Cheers,
Anders

-- 
Anders Darander
ChargeStorm AB / eStorm AB