Adding Android.bp file for new imported crate indexmap. am: a2798a33e9

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/indexmap/+/2164313

Change-Id: Iec91c04653bdc5049ea5124a8c9e3e930a50f74c
Signed-off-by: Automerger Merge Worker <[email protected]>