add argument to invocation to get returncode 0 for both connext 5.2.4…

[mikaelarguedas]

… and 5.3.0

I was looking into why my local builds became so much slower since I switched to connext 5.3.0.
The part that seems much slower is the invocation of the rtiddsgen_server executable in the Connext cmake module.

While I haven't found yet how to improve the speed in the invocation of the generator (they seem to be just as fast when running them in a shell), I noticed that none of our builds were using the ddsgen_server since we upgraded. The reason is that the return code when invoking the executable without argument is not the same between 5.2.X and 5.3.0.
Adding the -version argument seems to bring us back to both returning the code 0.

You can confirm it by looking for "/bin/rtiddsgen" in:
the last nightly: http://ci.ros2.org/view/nightly/job/nightly_linux_debug/602/consoleFull
the job with this change: http://ci.ros2.org/job/ci_linux/3295/consoleFull

[mikaelarguedas]

Ok looking a bit more into this it looks like the executable rtiddsgen_server behaves differently between 5.2.X and 5.3.0.

5.2.X it fails earlier if not passed any argument:
5.2.3:

• no arguments:

real	0m0.197s
user	0m0.008s
sys	0m0.004s

• with -version:

real	0m0.705s
user	0m0.004s
sys	0m0.008s

For connext 5.3.0 it seems to be roughly the same time:

• no arguments:

real	0m0.525s
user	0m0.000s
sys	0m0.012s

• with -version:

real	0m0.453s
user	0m0.004s
sys	0m0.008s

When running the same commands through CMake execute_process():

• 5.2.3:
  • no arguments: <1sec
  • with -version: ~20sec
• 5.3.0:
  • no arguments: ~20sec
  • with -version: ~20sec

So that's where the slow down in the CMake configure step comes from. Not sure what we can do in CMake to speed that up. I think this PR should be merged as is to allow the use of rtiddsgen_server on our current CIs. If I find a workaround to reduce the execution time I'll open a follow-up PR

[mikaelarguedas]

Note to self: We don't use rtiddsgen_server on MacOS because the executable doesnt seem to be there in 5.3.0 (but is present in 5.2.3)

[mikaelarguedas]

Final note on this: RTI confirmed that they don't support or ship rtiddsgen_server for Mac as of 5.3.0. There was a hiccup and it did not make it to the release notes