Add test infrastructure for running the arch mutator

Add TestArchConfig and NewTestArchContext to create a test context
that will run the arch mutator, which is necessary to test any code
that is inside a ctx.Device() block or similar.

Test: next patch
Change-Id: Ieb1a0326bc27fc18ba88b8d37655a7e0c6870d6c

android/config.go

@@ -185,6 +185,25 @@ func TestConfig(buildDir string) Config {
 	return Config{config}
 }
 
+// TestConfig returns a Config object suitable for using for tests that need to run the arch mutator
+func TestArchConfig(buildDir string) Config {
+	testConfig := TestConfig(buildDir)
+	config := testConfig.config
+
+	config.Targets = map[OsClass][]Target{
+		Device: []Target{
+			{Android, Arch{ArchType: Arm64, Native: true}},
+			{Android, Arch{ArchType: Arm, Native: true}},
+		},
+		Host: []Target{
+			{BuildOs, Arch{ArchType: X86_64}},
+			{BuildOs, Arch{ArchType: X86}},
+		},
+	}
+
+	return testConfig
+}
+
 // New creates a new Config object.  The srcDir argument specifies the path to
 // the root source directory. It also loads the config file, if found.
 func NewConfig(srcDir, buildDir string) (Config, error) {

android/mutator.go

@@ -78,11 +78,13 @@ var preArch = []RegisterMutatorFunc{
 	RegisterDefaultsPreArchMutators,
 }
 
+func registerArchMutator(ctx RegisterMutatorsContext) {
+	ctx.BottomUp("arch", archMutator).Parallel()
+	ctx.TopDown("arch_hooks", archHookMutator).Parallel()
+}
+
 var preDeps = []RegisterMutatorFunc{
-	func(ctx RegisterMutatorsContext) {
-		ctx.BottomUp("arch", archMutator).Parallel()
-		ctx.TopDown("arch_hooks", archHookMutator).Parallel()
-	},
+	registerArchMutator,
 }
 
 var postDeps = []RegisterMutatorFunc{

android/testing.go

@@ -27,6 +27,12 @@ func NewTestContext() *TestContext {
 	}
 }
 
+func NewTestArchContext() *TestContext {
+	ctx := NewTestContext()
+	ctx.preDeps = append(ctx.preDeps, registerArchMutator)
+	return ctx
+}
+
 type TestContext struct {
 	*blueprint.Context
 	preArch, preDeps, postDeps []RegisterMutatorFunc