Export variant/features via soong_injection

Test: build/bazel/ci/bp2build.sh
Change-Id: If70043dc9d020d5f4a243ba4b192b99c9c7e8563
diff --git a/bp2build/conversion.go b/bp2build/conversion.go
index 96c12d3..3ab846b 100644
--- a/bp2build/conversion.go
+++ b/bp2build/conversion.go
@@ -28,6 +28,8 @@
 
 	files = append(files, newFile("product_config", "soong_config_variables.bzl", cfg.Bp2buildSoongConfigDefinitions.String()))
 
+	files = append(files, newFile("product_config", "arch_configuration.bzl", android.StarlarkArchConfigurations()))
+
 	apiLevelsContent, err := json.Marshal(android.GetApiLevelsMap(cfg))
 	if err != nil {
 		panic(err)
diff --git a/bp2build/conversion_test.go b/bp2build/conversion_test.go
index 629ca9b..c94a923 100644
--- a/bp2build/conversion_test.go
+++ b/bp2build/conversion_test.go
@@ -103,6 +103,10 @@
 			basename: "soong_config_variables.bzl",
 		},
 		{
+			dir:      "product_config",
+			basename: "arch_configuration.bzl",
+		},
+		{
 			dir:      "api_levels",
 			basename: GeneratedBuildFileName,
 		},