Add RuleBuilder helper functions for built and prebuilt tools

Replace the common pattern of:
cmd.Tool(ctx.Config().HostToolPath(ctx, "tool"))
with:
cmd.BuiltTool("tool")

And similarly for PrebuiltBuildTool.

Test: m checkbuild
Change-Id: I7d63188505362c7df6a3b3e7330b4a2cca5a2409
diff --git a/java/dexpreopt_bootjars.go b/java/dexpreopt_bootjars.go
index fe468a9..4ef5bcf 100644
--- a/java/dexpreopt_bootjars.go
+++ b/java/dexpreopt_bootjars.go
@@ -229,7 +229,7 @@
 	if image.zip != nil {
 		rule := android.NewRuleBuilder()
 		rule.Command().
-			Tool(ctx.Config().HostToolPath(ctx, "soong_zip")).
+			BuiltTool(ctx, "soong_zip").
 			FlagWithOutput("-o ", image.zip).
 			FlagWithArg("-C ", image.dir.String()).
 			FlagWithInputList("-f ", allFiles, " -f ")
@@ -438,7 +438,7 @@
 		rule := android.NewRuleBuilder()
 		rule.Command().
 			// TODO: for now, use the debug version for better error reporting
-			Tool(ctx.Config().HostToolPath(ctx, "oatdumpd")).
+			BuiltTool(ctx, "oatdumpd").
 			FlagWithInputList("--runtime-arg -Xbootclasspath:", image.dexPaths.Paths(), ":").
 			FlagWithList("--runtime-arg -Xbootclasspath-locations:", image.dexLocations, ":").
 			FlagWithArg("--image=", dexpreopt.PathToLocation(image.images[arch], arch)).Implicit(image.images[arch]).