[clang] [Driver] Don't pass -Z to ld for ELF platforms (PR #69120)

[Brad Smith via cfe-commits]

brad0 wrote:

OpenBSD has a -Z flag for our BFD linker.

```-Z        Produce 'Standard' executables, disables Writable XOR Executable features in resulting binaries.```

https://github.com/openbsd/src/commit/0abdc3723b5d33dde698ab941325edec2819c128
https://github.com/openbsd/src/commit/58cb065838343f5d972d625775790ebb89f56d88
https://github.com/openbsd/src/commit/0bd5fc2a33971fd1cca748eda19e75844fa9c27a

But it was never ported to our copy of LLD, which is what almost all of our Clang switched archs use, plus I can't seem to find any use of the flag anywhere nowadays.

https://github.com/llvm/llvm-project/pull/69120