Export default apex version from updatable_modules.go to Bazel's
apex_toolchain through soong_injection.

This is necessary to keep both Bazel and Soong in sync.

Test: presubmit
Bug: 238723069
Fixes: 238153998

Change-Id: Ibf4a8ed91d358dc7800c10e4112485a52f0606bb
diff --git a/bp2build/conversion_test.go b/bp2build/conversion_test.go
index b0d0740..0cb711c 100644
--- a/bp2build/conversion_test.go
+++ b/bp2build/conversion_test.go
@@ -104,6 +104,14 @@
 			basename: "constants.bzl",
 		},
 		{
+			dir:      "apex_toolchain",
+			basename: GeneratedBuildFileName,
+		},
+		{
+			dir:      "apex_toolchain",
+			basename: "constants.bzl",
+		},
+		{
 			dir:      "metrics",
 			basename: "converted_modules.txt",
 		},