I’m happy to report that the Eclipse SDK integration builds starts in less than 5 seconds (~4900 ms) on my machine into an empty workspace.
IIRC this used to be around 9 seconds 2 years ago. 4.13 (which was already quite a bit improved used around 5800ms
(6887ms with EGit and Marketplace).
For recent improvements in this release see https://bugs.eclipse.org/bugs/show_bug.cgi?id=550136
Thanks to everyone who contributed.