[clang] [RISCV] Set __GCC_CONSTRUCTIVE_SIZE/__GCC_DESTRUCTIVE_SIZE to 64 for riscv64 (PR #162986)

[Pengcheng Wang via cfe-commits]

wangpc-pp wrote:

> Reverse ping - I'd like to see this move forward.

I don't know if we have a consensus about the value here, is it OK to set values to 64 for both RV32 and RV64?

https://github.com/llvm/llvm-project/pull/162986