Ensure CC GC is used for the read barrier config.

To prevent the -Xgc option from causing unsupported GC types to run.

Bug: 12687968
Test: test-art-host with CC.
Change-Id: I10b42190c0888342e9127c52e863ddae82e4d7a1
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index 6d849c4..a1b6866 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -1023,8 +1023,10 @@
                        runtime_options.GetOrDefault(Opt::NonMovingSpaceCapacity),
                        runtime_options.GetOrDefault(Opt::Image),
                        runtime_options.GetOrDefault(Opt::ImageInstructionSet),
-                       xgc_option.collector_type_,
-                       runtime_options.GetOrDefault(Opt::BackgroundGc),
+                       // Override the collector type to CC if the read barrier config.
+                       kUseReadBarrier ? gc::kCollectorTypeCC : xgc_option.collector_type_,
+                       kUseReadBarrier ? BackgroundGcOption(gc::kCollectorTypeCCBackground)
+                                       : runtime_options.GetOrDefault(Opt::BackgroundGc),
                        runtime_options.GetOrDefault(Opt::LargeObjectSpace),
                        runtime_options.GetOrDefault(Opt::LargeObjectThreshold),
                        runtime_options.GetOrDefault(Opt::ParallelGCThreads),