[llvm] [Android] Drop workarounds for older Android API levels pre 9, 17 and 21 (PR #161911)

[Shoaib Meenai via llvm-commits]

smeenai wrote:

Thanks for flagging this! We recently moved to API 21+ for all our major apps (and I'm delighted to not have to support anything older anymore), so this should be okay on our end now :)

https://github.com/llvm/llvm-project/pull/161911