Add method to determine variations from a Target

The arch variants are hardcoded in every module type.  Refactor
them out into a Target.Variations() method in preparation for
splitting the arch mutator into two, which will require using
different variations.

Test: m checkbuild
Change-Id: I28ef7cd5168095ac888fe77f04e27f9ad81978c0
diff --git a/java/app.go b/java/app.go
index e033661..6b640f1 100644
--- a/java/app.go
+++ b/java/app.go
@@ -167,10 +167,8 @@
 
 	embedJni := a.shouldEmbedJnis(ctx)
 	for _, jniTarget := range ctx.MultiTargets() {
-		variation := []blueprint.Variation{
-			{Mutator: "arch", Variation: jniTarget.String()},
-			{Mutator: "link", Variation: "shared"},
-		}
+		variation := append(jniTarget.Variations(),
+			blueprint.Variation{Mutator: "link", Variation: "shared"})
 		tag := &jniDependencyTag{
 			target: jniTarget,
 		}
diff --git a/java/device_host_converter.go b/java/device_host_converter.go
index 030b010..14db521 100644
--- a/java/device_host_converter.go
+++ b/java/device_host_converter.go
@@ -18,8 +18,6 @@
 	"fmt"
 	"io"
 
-	"github.com/google/blueprint"
-
 	"android/soong/android"
 )
 
@@ -83,13 +81,13 @@
 var deviceHostConverterDepTag = dependencyTag{name: "device_host_converter"}
 
 func (d *DeviceForHost) DepsMutator(ctx android.BottomUpMutatorContext) {
-	variation := []blueprint.Variation{{Mutator: "arch", Variation: "android_common"}}
-	ctx.AddFarVariationDependencies(variation, deviceHostConverterDepTag, d.properties.Libs...)
+	ctx.AddFarVariationDependencies(ctx.Config().AndroidCommonTarget.Variations(),
+		deviceHostConverterDepTag, d.properties.Libs...)
 }
 
 func (d *HostForDevice) DepsMutator(ctx android.BottomUpMutatorContext) {
-	variation := []blueprint.Variation{{Mutator: "arch", Variation: ctx.Config().BuildOsCommonVariant}}
-	ctx.AddFarVariationDependencies(variation, deviceHostConverterDepTag, d.properties.Libs...)
+	ctx.AddFarVariationDependencies(ctx.Config().BuildOSCommonTarget.Variations(),
+		deviceHostConverterDepTag, d.properties.Libs...)
 }
 
 func (d *DeviceHostConverter) GenerateAndroidBuildActions(ctx android.ModuleContext) {
diff --git a/java/device_host_converter_test.go b/java/device_host_converter_test.go
index 44aae9b..3c9a0f3 100644
--- a/java/device_host_converter_test.go
+++ b/java/device_host_converter_test.go
@@ -60,7 +60,7 @@
 	deviceImportModule := ctx.ModuleForTests("device_import_module", "android_common")
 	deviceImportCombined := deviceImportModule.Output("combined/device_import_module.jar")
 
-	hostModule := ctx.ModuleForTests("host_module", config.BuildOsCommonVariant)
+	hostModule := ctx.ModuleForTests("host_module", config.BuildOSCommonTarget.String())
 	hostJavac := hostModule.Output("javac/host_module.jar")
 	hostRes := hostModule.Output("res/host_module.jar")
 	combined := hostModule.Output("combined/host_module.jar")
@@ -133,11 +133,11 @@
 
 	ctx, config := testJava(t, bp)
 
-	hostModule := ctx.ModuleForTests("host_module", config.BuildOsCommonVariant)
+	hostModule := ctx.ModuleForTests("host_module", config.BuildOSCommonTarget.String())
 	hostJavac := hostModule.Output("javac/host_module.jar")
 	hostRes := hostModule.Output("res/host_module.jar")
 
-	hostImportModule := ctx.ModuleForTests("host_import_module", config.BuildOsCommonVariant)
+	hostImportModule := ctx.ModuleForTests("host_import_module", config.BuildOSCommonTarget.String())
 	hostImportCombined := hostImportModule.Output("combined/host_import_module.jar")
 
 	deviceModule := ctx.ModuleForTests("device_module", "android_common")
diff --git a/java/java.go b/java/java.go
index 4264ba9..47fb1a7 100644
--- a/java/java.go
+++ b/java/java.go
@@ -546,9 +546,7 @@
 	ctx.AddVariationDependencies(nil, libTag, j.properties.Libs...)
 	ctx.AddVariationDependencies(nil, staticLibTag, j.properties.Static_libs...)
 
-	ctx.AddFarVariationDependencies([]blueprint.Variation{
-		{Mutator: "arch", Variation: ctx.Config().BuildOsCommonVariant},
-	}, pluginTag, j.properties.Plugins...)
+	ctx.AddFarVariationDependencies(ctx.Config().BuildOSCommonTarget.Variations(), pluginTag, j.properties.Plugins...)
 
 	android.ProtoDeps(ctx, &j.protoProperties)
 	if j.hasSrcExt(".proto") {