Fix dist(s)-with-tag and add tests to prevent regression.

While AndroidMkEntries' DistFiles were populated from java_library
properly, there was a bug in the conditionals that dropped the tagged
DistFiles.

Fixes b/152834186
Fixes b/161339864

Test: soong tests, m sdk dist (creates out/dist/test.jar with
aosp/1363578)

Signed-off-by: Jingwen Chen <jingwen@google.com>
Exempt-From-Owner-Approval: cherry-pick from master
Change-Id: Id895282256fd367b2f46dcb7a643465fa66c9456
Merged-In: Id895282256fd367b2f46dcb7a643465fa66c9456
(cherry picked from commit 8481186d56)

android/androidmk.go

@@ -185,7 +185,7 @@ func (a *AndroidMkEntries) GetDistForGoals(mod blueprint.Module) []string {
 	var ret []string
 
 	availableTaggedDists := TaggedDistFiles{}
-	if a.DistFiles != nil && len(a.DistFiles[""]) > 0 {
+	if a.DistFiles != nil {
 		availableTaggedDists = a.DistFiles
 	} else if a.OutputFile.Valid() {
 		availableTaggedDists = MakeDefaultDistFiles(a.OutputFile.Path())

android/androidmk_test.go

@@ -45,6 +45,8 @@ func (m *customModule) OutputFiles(tag string) (Paths, error) {
 		return PathsForTesting("one.out"), nil
 	case ".multiple":
 		return PathsForTesting("two.out", "three/four.out"), nil
+	case ".another-tag":
+		return PathsForTesting("another.out"), nil
 	default:
 		return nil, fmt.Errorf("unsupported module reference tag %q", tag)
 	}
@@ -119,6 +121,38 @@ func TestGetDistForGoals(t *testing.T) {
 				"$(call dist-for-goals,my_goal,one.out:one.out)\n",
 			},
 		},
+		{
+			bp: `
+			custom {
+				name: "foo",
+				dist: {
+					targets: ["my_goal"],
+					tag: ".another-tag",
+				}
+			}
+			`,
+			expectedAndroidMkLines: []string{
+				".PHONY: my_goal\n",
+				"$(call dist-for-goals,my_goal,another.out:another.out)\n",
+			},
+		},
+		{
+			bp: `
+			custom {
+				name: "foo",
+				dists: [
+					{
+						targets: ["my_goal"],
+						tag: ".another-tag",
+					},
+				],
+			}
+			`,
+			expectedAndroidMkLines: []string{
+				".PHONY: my_goal\n",
+				"$(call dist-for-goals,my_goal,another.out:another.out)\n",
+			},
+		},
 		{
 			bp: `
 			custom {