sablevm's JAVA_HOME is located within an arch's /usr/[lib|lib64] directory. Currently the java-vm-2 eclass does not parse the env file to replace any references to LIBDIR to the env file. As this is arch dependent it should be handled within the eclass.
Created attachment 108107 [details, diff] patch to replace @LIBDIR@ in vm's env file with the current arch's lib dir
If this is only needed by sablevm than no need and we can close bug. From the looks it seems generic so would still have use once sablevm is gone.
http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/eclass/java-vm-2.eclass?r1=1.29&r2=1.30