[clang] [llvm] [RISCV][FMV] Support target_clones (PR #85786)

[Craig Topper via llvm-commits]

topperc wrote:

> The proposal can be found at the [riscv-non-isa/riscv-c-api-doc#48](https://github.com/riscv-non-isa/riscv-c-api-doc/pull/48).

Please put this in the PR description

https://github.com/llvm/llvm-project/pull/85786