[BRLTTY] error after i run make / keycodes description

[Stéphane Doyon]

On Thu, 28 Nov 2019, Dave Mielke wrote:

> Your brlapi_constants.h is nearly empty. It should be much larger - mine has a
> little over 400 lines in it. This looks very similar to a problem that was
> reported, here, about a week ago. The problem was that some of the awk scripts
> that building brltty uses were compatible with gawk but not with mawk. What
> does the AWK = line in config.mk say?
>
> This problem has now been fixed. Please, therefore, get the latest brltty
> development source and give it another try.

I'm not sure if this regressed, but I'm encountering this problem again, 
building at head as of right now on Raspbian Buster.
And

sudo apt install gawk

fixed it.