The compilation of the hotspot compiler failes because it uses uname to determine if it will work on the target platform. Linux 3 is not allowed yet (and this approach also breaks in many situations, see http://blog.flameeyes.eu/2011/09/02/buildsystem-quirks-now-you-know-why-you-don-t-rely-on-uname for details).
The best solution is to disable the checking by calling emake (in src_compile) like this:
DISABLE_HOTSPOT_OS_VERSION_CHECK=ok emake -j 1
Created attachment 286901 [details]
Created attachment 286903 [details]
Affects me too. I attached build log and emerge --info output for completeness.
I get this message:
*** This OS is not supported: Linux sed-notebook 3.0.4-gentoo
So the bug could be confirmed, I daresay?
*** This bug has been marked as a duplicate of bug 380205 ***