Improve deterministic boot image compilation with CC collector.

Allow deterministic compilation with the read barrier configuration.

Test: Compare boot.art produced by different builds of the same tree.
Bug: 37442966
Change-Id: I6cc0d0d7fdfe4f954765764d9f7f3778b7307028
diff --git a/build/art.go b/build/art.go
index 053968d..61a9759 100644
--- a/build/art.go
+++ b/build/art.go
@@ -59,8 +59,8 @@
 	}
 
 	if !envFalse(ctx, "ART_USE_READ_BARRIER") && ctx.AConfig().ArtUseReadBarrier() {
-		// Used to change the read barrier type. Valid values are BAKER, BROOKS, TABLELOOKUP.
-		// The default is BAKER.
+		// Used to change the read barrier type. Valid values are BAKER, BROOKS,
+		// TABLELOOKUP. The default is BAKER.
 		barrierType := envDefault(ctx, "ART_READ_BARRIER_TYPE", "BAKER")
 		cflags = append(cflags,
 			"-DART_USE_READ_BARRIER=1",