Builders on ews-build don't need to run clean builds. Incremental builds are fine for EWS. clean builds take a lot longer without much value addition for EWS. Old EWS also doesn't run clean builds, ews-build should do the same.
ews-build is currently running clean builds (even though we have not explicitly specified clean build in our configuration).
To elaborate on old EWS behavior, it dies build clean when retrying. Otherwise, changes that require clean rebuild would be breaking EWS permanently, until manual intervention.
(In reply to Alexey Proskuryakov from comment #1)
> To elaborate on old EWS behavior, it does build clean when retrying.
> Otherwise, changes that require clean rebuild would be breaking EWS permanently, until manual intervention.
Yes, we will continue to do clean build on retry (unapply-patch step removes untracked files including WebKitBuild directory).
Created attachment 367387 [details]
Comment on attachment 367387 [details]
View in context: https://bugs.webkit.org/attachment.cgi?id=367387&action=review
> + file is present, during the Source checkout, Buildbot clean the working directory completely (including removing
nit: buildbot cleans
Committed r244283: <https://trac.webkit.org/changeset/244283>