[swift-dev] Turns out Incremental builds were not actually incremental

[Michael Gottesman]

I believe we do trash the module cache folder.

> On Jul 21, 2016, at 3:46 PM, Jordan Rose <jordan_rose at apple.com> wrote:
> 
> 
>> On Jul 21, 2016, at 15:06, Michael Gottesman <mgottesman at apple.com> wrote:
>> 
>> 
>>> On Jul 21, 2016, at 2:54 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>>> 
>>> IIRC this was deliberate because of some past issues with things not getting rebuilt. In particular, even an incremental build should trash the module cache folder every build, and I don’t think we do this. Nicole, do you remember specifically why this was changed? (Or Mishal, when back from vacation?)
>> 
>> The problem IIRC actually had to do with cloning ninja without checking if we had already checked it out. I updated the bots to do a check if the directory exists before attempting to clone it.
> 
> Okay, but if we don’t trash the module cache folder every build, we’re going to see problems with apinotes.
> 
> Jordan
>