Split ArchMutatorContext out of BaseMutatorContext

Split the context methods that are useful on anything visiting a
module that has arch variants into a separate ArchMutatorContext
for reuse by TranstitionMutators.

Bug: 319288033
Test: builds
Change-Id: Ifdc21983c6c79f22965a49f169812a8cc3ad975b

android/arch_module_context.go

@@ -0,0 +1,83 @@
+// Copyright 2024 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package android
+
+// ArchModuleContext can be embedded in other contexts to provide information about the module set by
+// the archMutator.
+type ArchModuleContext interface {
+	Target() Target
+	TargetPrimary() bool
+
+	// The additional arch specific targets (e.g. 32/64 bit) that this module variant is
+	// responsible for creating.
+	MultiTargets() []Target
+	Arch() Arch
+	Os() OsType
+	Host() bool
+	Device() bool
+	Darwin() bool
+	Windows() bool
+	PrimaryArch() bool
+}
+
+type archModuleContext struct {
+	// TODO: these should eventually go through a (possibly cached) provider like any other configuration instead
+	//  of being special cased.
+	os            OsType
+	target        Target
+	targetPrimary bool
+	multiTargets  []Target
+	primaryArch   bool
+}
+
+func (a *archModuleContext) Target() Target {
+	return a.target
+}
+
+func (a *archModuleContext) TargetPrimary() bool {
+	return a.targetPrimary
+}
+
+func (a *archModuleContext) MultiTargets() []Target {
+	return a.multiTargets
+}
+
+func (a *archModuleContext) Arch() Arch {
+	return a.target.Arch
+}
+
+func (a *archModuleContext) Os() OsType {
+	return a.os
+}
+
+func (a *archModuleContext) Host() bool {
+	return a.os.Class == Host
+}
+
+func (a *archModuleContext) Device() bool {
+	return a.os.Class == Device
+}
+
+func (a *archModuleContext) Darwin() bool {
+	return a.os == Darwin
+}
+
+func (a *archModuleContext) Windows() bool {
+	return a.os == Windows
+}
+
+func (b *archModuleContext) PrimaryArch() bool {
+	return b.primaryArch
+}