[lworld] [AArch64] TestLWorld.java assertion failure in OopFlow::build_oop_map

This happens reliably in TestLWorld::test9() scenario 0 on AArch64:

# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/mnt/nicgas01-pc/valhalla/src/hotspot/share/opto/buildOopMap.cpp:360), pid=8866, tid=8882
# assert(false) failed: there should be a oop in OopMap instead of a live raw oop at safepoint
#