Merge "aconfig: CodegenMode::Exported: only generate code for exported flags" into main am: 3f2432967b

Original change: https://android-review.googlesource.com/c/platform/build/+/2873755

Change-Id: I481d6cd1c6646e6251aecc044f843329d2323079
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>