Use LoadHook to create modules in java_sdk_library

Creating new modules in a mutator is dangerous, as other mutators
that need to see the new modules may already have run, in this case
the prebuilts mutator.  Move SdkLibraryMutator to a LoadHook instead.
Also moves registering the LoadHook mutator to testing.go so it is
registered for all tests.

Test: m checkbuild
Change-Id: I08bd76a0e6205d2ca27861058067a1562c339eed

android/hooks.go

@@ -123,6 +123,10 @@ type hooks struct {
 	install []func(InstallHookContext)
 }
 
+func registerLoadHookMutator(ctx RegisterMutatorsContext) {
+	ctx.TopDown("load_hooks", LoadHookMutator).Parallel()
+}
+
 func LoadHookMutator(ctx TopDownMutatorContext) {
 	if m, ok := ctx.Module().(Module); ok {
 		// Cast through *androidTopDownMutatorContext because AppendProperties is implemented

android/mutator.go

@@ -73,9 +73,7 @@ type RegisterMutatorsContext interface {
 type RegisterMutatorFunc func(RegisterMutatorsContext)
 
 var preArch = []RegisterMutatorFunc{
-	func(ctx RegisterMutatorsContext) {
-		ctx.TopDown("load_hooks", LoadHookMutator).Parallel()
-	},
+	registerLoadHookMutator,
 	RegisterNamespaceMutator,
 	RegisterPrebuiltsPreArchMutators,
 	RegisterDefaultsPreArchMutators,

android/testing.go

@@ -37,6 +37,8 @@ func NewTestContext() *TestContext {
 
 	ctx.SetNameInterface(nameResolver)
 
+	ctx.preArch = append(ctx.preArch, registerLoadHookMutator)
+
 	ctx.postDeps = append(ctx.postDeps, registerPathDepsMutator)
 
 	return ctx