[lld] [LLD][SPARC] Implement enough functionality to run non-trivial 64-bit programs (PR #137919)

[Fangrui Song via llvm-commits]

MaskRay wrote:

(On a trip with limited computer access. Response may be delayed)

> I haven't had time to write any tests for this yet, unfortunately. But the changes are straightforward enough that they should be reviewable at least, and as mentioned, real and non-trivial programs actually work with this.

Tests are required to make this PR acceptable. You might git log lld/ELF/Arch/PPC.cpp/RISCV.cpp and check how I added initial tests for PPC and PIC RISCV.

https://github.com/llvm/llvm-project/pull/137919