[clang] [clang] Define SwiftInfo for RISCVTargetCodeGenInfo (PR #82152)

[Jessica Clarke via cfe-commits]

jrtc27 wrote:

What purpose does this serve if swiftcall doesn't work? Given the tests only test that you can produce IR from Clang, that suggests that it doesn't actually do anything useful?.. (And if it does do something useful, *that* should be being tested)

https://github.com/llvm/llvm-project/pull/82152