The fix has already been applied, but I'm opening a JIRA to document this to make it easier for any users of 2.9.1 who encounter the problem to figure out what to do.
Jikes RVM 2.9.1 is setup to use ECJ 3.3. ECJ 3.3 has a bug that causes problems when building the Jikes RVM bootimage using HotSpot as the host JVM. In particular, ECJ 3.3 building Classpath where it generates an incorrect line number map in java.util.zip.InflaterDynHeader's static initializer. This bug incorrectly fails the HotSpot bytecode verifier and causes HotSpot builds to fail during a Class.forName in the boot image writer.
The workaround is simply to use ECJ 3.2 instead (http://jikesrvm.svn.sourceforge.net/viewvc/jikesrvm?view=rev&revision=12920).