We can't just edit binary wrappers in place because of a length
mismatch, so we have to parse the generating makeCWrapper call out of
the binary, extract wrapper arguments from it and add them to the
Firefox wrapper.
All these contortions are needed because Firefox looks for its runtime
in argv0, so the proper argv0 needs to be set by wrappers to always
point to the "final" runtime. I think this could be avoided by wrapping
/lib/$libName/firefox instead of /bin/firefox, and I'd like to look into
that in the future, but for now I'm just fixing the immediate problem.
863cdf8f09