[lld] [ELF] PHDRS update while condition and phdrs.s unclose2.lds output (PR #100918)

[Fangrui Song via llvm-commits]

MaskRay wrote:

Perhaps `readNameTill` can be added: it behaves like `till`, but it expects that token to be a NAME (identifier of quoted string). If `(` `)` `}` is encountered, report an error. This function will allows us to remove a few `unquote(tok)`.

Then this PR can be updated to use `readNameTill`

https://github.com/llvm/llvm-project/pull/100918