I made an attempt at building Firefox 20, but it looks for the non-existent file ../../media/webrtc/trunk/src/modules/modules_aecm_neon/libaecm_neon.a. Google seems to know nothing about libaecm. It does find webrtc, but so far I haven't found anything helpful there. I don't see a way to build without webrtc or influence how it is built.
There is a separate package webrtc-audio-processing in portage, but it is hard masked. Portage doesn't list it as something needed, so it seems that webrtc is part of the Firefox 20 code.
Is this another case of developers assuming no one uses armv6 anymore?
Thanks for any clues!