[lld] [lld][WebAssembly] Move command-line option defaults into Config.h. NFC (PR #227911)

[Sam Clegg via llvm-commits]

sbc100 wrote:

@MaskRay I'm curious what you think about this approach.     Assuming you like the idea I can do the same thing for the other linkers.    

https://github.com/llvm/llvm-project/pull/227911