riscv64: small fixes for gdb workflow

Test: build, sync, run, then GDB

  $ art/tools/buildbot-build.sh --target --installclean
  $ art/tools/buildbot-cleanup-device.sh
  $ art/tools/buildbot-setup-device.sh
  $ art/tools/buildbot-sync.sh
  $ art/test/run-test --chroot $ART_TEST_CHROOT --64 -O --never-clean --no-relocate --no-image 001-HelloWorld
  $ art/tools/buildbot-vm.sh connect
  % unshare --user --map-root-user chroot art-test-chroot
  % cd /data/run-test/test-986090
  % cat run.sh
  % (paste env export commands)
  % gdb --args <paste command>

Change-Id: I4a929ba9dab353507e08ae648558b6282576b498
2 files changed