[LSC] Add LOCAL_LICENSE_KINDS to external/Reactive-Extensions/RxCpp am: 6e6c469a7c am: c17d041feb am: 234f2f2fda am: 5f4c3264fe

Original change: https://android-review.googlesource.com/c/platform/external/Reactive-Extensions/RxCpp/+/1588615

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I2bae3090f74c116b3aec784a8203389c42447e61