Change type of Unbundled_build_apps from bool to []string

Unbundled_build_apps is supposed to be a list of apps to
build as unbundled, not just a simple boolean. Change it
to properly reflect what it is, because the starlark
product configuration relies on soong's interpretation
of variables types.

Bug: 201700692
Test: Presubmits
Change-Id: I85d40d58fe519f9f6e5a382b8f3ec9014f990aa1

android/config.go

@@ -856,7 +856,7 @@ func (c *config) UnbundledBuild() bool {
 // Returns true if building apps that aren't bundled with the platform.
 // UnbundledBuild() is always true when this is true.
 func (c *config) UnbundledBuildApps() bool {
-	return Bool(c.productVariables.Unbundled_build_apps)
+	return len(c.productVariables.Unbundled_build_apps) > 0
 }
 
 // Returns true if building image that aren't bundled with the platform.

android/variable.go

@@ -15,13 +15,14 @@
 package android
 
 import (
-	"android/soong/android/soongconfig"
-	"android/soong/bazel"
 	"fmt"
 	"reflect"
 	"runtime"
 	"strings"
 
+	"android/soong/android/soongconfig"
+	"android/soong/bazel"
+
 	"github.com/google/blueprint/proptools"
 )
 
@@ -247,7 +248,7 @@ type productVariables struct {
 
 	Allow_missing_dependencies   *bool    `json:",omitempty"`
 	Unbundled_build              *bool    `json:",omitempty"`
-	Unbundled_build_apps         *bool `json:",omitempty"`
+	Unbundled_build_apps         []string `json:",omitempty"`
 	Unbundled_build_image        *bool    `json:",omitempty"`
 	Always_use_prebuilt_sdks     *bool    `json:",omitempty"`
 	Skip_boot_jars_check         *bool    `json:",omitempty"`