Merge "Add hidl-gen to build tools" am: 3fcde0a898 am: b62a14a1e6 am: 69406c2a7b am: f0fde02d4a am: 7c351359fb

Original change: https://android-review.googlesource.com/c/platform/prebuilts/build-tools/+/1421851

Change-Id: Ic6e55d98ee4c7cc448d728d82ea2890d22fce0ba