Add release_config_contributions modules

These are used to enumerate what directories may contribute to release
configs, whether or not they are actually used in the build.

Bug: b/370544058
Test: manual, TH
Change-Id: I1509eb3795a9b51b29995b182b77ade76021bb52
diff --git a/aconfig/build_flags/Android.bp b/aconfig/build_flags/Android.bp
index be1b872..139aeac 100644
--- a/aconfig/build_flags/Android.bp
+++ b/aconfig/build_flags/Android.bp
@@ -17,6 +17,7 @@
         "build_flags_singleton.go",
         "declarations.go",
         "init.go",
+        "release_configs.go",
     ],
     testSrcs: [
     ],