BUILD: makefile: enable TFO on linux platforms

TCP Fast Open is supported on all supported Linux kernels and on all
kernels shipped in supported distros, except the older 2.6.32 that
comes with RHEL6. However the option is harmless, will not prevent
from building and smoothly falls back even if forcefully enabled, so
it makes sense to enable it by default. It's still possible to pass
"USE_TFO=" to force it disabled if really desired.
1 file changed