Sorry for this happening again in RC2.
The cause is that Tycho 1.2.0-SNAPSHOT, used to build Eclipse Platform, now support Java 10 and publish newer a.jre.javase IUs.
As adopters facing this issue (if you do face this issue), here are various possible fixes you can try:
as reported by Jonah, if you're using a target platform in 'planner'
mode you can simply replace the version of the *a.jre.javase units to
0.0.0 so it will just resolve at best and wouldn't need to be change when a newer a.jre.javase arrives
* You can simply update the version of the a.jre.javase IU to 10.0.0 in your .target file if building against Platform 4.8.RC2
* You can try Tycho 1.2.0-SNAPSHOT and remove references to a.jre.javase IU (not sure that would work is your .target file is a 'slicer')
There is one related bug in Eclipse Platform https://bugs.eclipse.org/bugs/show_bug.cgi?id=535219
. Platform didn't adapt properly to latest change in Tycho 1.2.0-SNAPSHOT. We're actively working on fixing this and have actually already used a workaround for RC2 so downstream should not be affected. A patch will be submitted in the next minutes, and I'm hopeful that this is the final step of a long story of an issue in dependency management for execution environment that spanned across years and several big bugs in multiple components and that was the cause of a lot of bug reports or required hacks. But it wasn't easy to get there and it required one of the biggest change in p2 that ever happened since p2 inception, which cascaded to a bunch of small glitches. I'm very hopeful that this one is the last one, that we won't talk again about this a.jre.javase unit for a while, and can bet drinks at upcoming EclipseCon France with those who are more skeptical ;)
Cheers, sorry for the disturbance, and happy continuation of release!