[BRLTTY] Minor build issue on brltty-6.9 branch

[Elias Oltmanns]

Hi there,

when I run

$ ./autogen
$ ./configure --prefix=/usr

the Lua bindings get installed under /usr/local, all the same. An early
symptom is this:

$ grep -r usr/local Bindings/
Bindings/Lua/Makefile:LUA_API_DIRECTORY = $(INSTALL_ROOT)/usr/local/lib/lua/5.4

As an aside, I originally set out to verify that Samuel's commit
14322dbf does indeed fix an issue I reported a few weeks ago. Even
though I managed to build BRLTTY from source, and make it work on the
console, Orca somehow fails (or does not even try to) connect to BRLTTY.
I have just asked for assistance with regard to that matter on the Orca
list and will report back here as soon as I have made progress.

Thanks for all your work and best wishes,

Elias