osmo-trx shouldn't run with address sanitizer. But omitting --enable-sanitize
from osmo-trx breaks 'make check', so then the whole top-level makefile will
end in error with sanitize.opts.
A user wanting to build osmo-trx can just uncomment that line.
Change-Id: I589f49652f8fa4e5becc7d7e63e6e4bc1a8b33bb