Add flag to unset use-ite-for-select

[hra687261]

See #611. I am open to suggestion for the flag name and where to place the global variable.

[redianthus]

I think the global variable is at a correct place. But after looking at the benchmarks, I'm tempted to say that ite is not the best default (and thus the flag should rather be --use-ite-for-select, sorry :sweat_smile:

[hra687261]

No problem, I just changed it.

[hra687261]

Looks like something with the new change significantly slows down the CI, I can change it back, or maybe we should investigate more in case in it a bug.

[redianthus]

@hra687261 we'll have to try to find the bug when you come back. Also this is conflicting with #801 but it'll be easy to fix (rebase and on the conflicting commit, simply regenerate the doc with dune runtest && dune promote).

[hra687261]

The culprit is dobble.c, simply running htop reveals it since it seems to take over 5 minutes or loop forever, the slowdown is reproducible with:

dune exec -- owi c -O1 doc/src/sap/dobble.c -w1 --no-value --no-assert-failure-expression-printing 

I will try to understand what is going on, but if you have the time you can take a look also @redianthus

[redianthus]

Thanks!