fix #14314 do not analyze importc procs for effects

[timotheecour]

fix #14314

[kaushalmodi]

@timotheecour This fix works beautifully! The std_vector tests seem to be sped up even more after this, may be because now it is not throwing the ProveInit warning for each importcpp proc.

[timotheecour]

good to hear!

The std_vector tests seem to be sped up

I did not expect that, can you double check with some benchmark? If merely issuing warnings has a measurable performance impact on compile times, we have a bigger problem lol

[kaushalmodi]

As I said "The std_vector tests seem to be sped up". I measured and there's not much noticeable difference. May be lesser noise on the stdout is giving a feeling that the tests ended sooner. Based on the CPU load, it takes 6-8 seconds to finish nim test on the std_vector repo.