[BRLTTY] standalone build and glibc

[Samuel Thibault]

Ok, the ground issue is that libpthread's initialization function does
not get called, and thus pthread operations get bogus behavior.  As I
said, Drepper doesn't care about static linking, and the pthread case
brings a lot of potential issues.  A workaround is to use
--whole-archive -lpthread --no-whole-archive to include it all.  Another
way is to automatically disable pthread detection when building a
standalone brltty.

Samuel