Use validations for blueprint tests

Pass -n to blueprint to make it use validation dependencies for tests,
which will let them run in parallel with soong_build.

Bug: 156428456
Test: m nothing
Change-Id: I706c14330543e2a7728e5dc385976900c67cb2f5
diff --git a/ui/build/soong.go b/ui/build/soong.go
index 749acb3..fb21430 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -38,7 +38,7 @@
 		ctx.BeginTrace(metrics.RunSoong, "blueprint bootstrap")
 		defer ctx.EndTrace()
 
-		cmd := Command(ctx, config, "blueprint bootstrap", "build/blueprint/bootstrap.bash", "-t")
+		cmd := Command(ctx, config, "blueprint bootstrap", "build/blueprint/bootstrap.bash", "-t", "-n")
 		cmd.Environment.Set("BLUEPRINTDIR", "./build/blueprint")
 		cmd.Environment.Set("BOOTSTRAP", "./build/blueprint/bootstrap.bash")
 		cmd.Environment.Set("BUILDDIR", config.SoongOutDir())