Allow all GCs when not using read barrier

Currently we are trying to force userfaultfd GC when
ART_USE_READ_BARRIER=false. But that doesn't work for targets attempting
to use semi-space GC.

Bug: 243181908
Test: ART_DEFAULT_GC_TYPE=SS ART_USE_READ_BARRIER=false
art/test/testrunner/testrunner.py --host

Change-Id: I0e17df4c7451bb627150ad9ca70030f315c4995f
5 files changed