[llvm] [SPIRV] Emitting DebugSource, DebugCompileUnit (PR #97558)

[Nathan Gauër via llvm-commits]

https://github.com/Keenuts commented:

Left some comments, a bit late on the review sorry for that.
One question:

When you'll have to handle object debug instruction, methods will require forward declaring some debug IDs. This means you'll have to use SPV_KHR_relaxed_extended_instruction
Do you have a plan to handle generating `OpExtInstWithForwardRefs` instead of `OpExtInst` in such cases?
(For DXC, we relied on a late pass which goes over the SPIR-V asm, and fixup the opcodes to be one or the other depending on the need.)

https://github.com/llvm/llvm-project/pull/97558