[llvm] MC: Refine ALIGN relocation conditions (PR #150816)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> I think "make linker synthesize ALIGN relocations at input section starts" would be my preference, otherwise -mno-relax objects will require relaxation support in the linker, which seems a bit odd (yes most linkers have support right now, but it still feels strange to require it)

Agreed. I have made a draft to synthesize ALIGN relocations at section start: https://github.com/MaskRay/llvm-project/pull/5

Created https://sourceware.org/bugzilla/show_bug.cgi?id=33236 ("ld riscv: Relocatable linking challenge with R_RISCV_ALIGN")

https://github.com/llvm/llvm-project/pull/150816