[clang] [Clang][Driver] Revise Cygwin ToolChain to call linker directly (PR #147960)

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jeremyd2019 wrote:

I was thinking that `-u` wouldn't do anything useful (and I'm still thinking that), but I just had a thought about why you might think it's necessary (or, why it might not work as expected).

`--wrap` renames the definition to `__real_X` and references to `__wrap_X`.  If libc++ has the operator new/delete declared as dllimport, the symbol involved would actually be `__imp_X`, which wouldn't be redirected by `--wrap`.  `-u` might be trying to force the inclusion of the jump stub, which would be wrapped.  But, `__imp_X` is still unwrapped and might be used directly.  Does this make sense?

https://github.com/llvm/llvm-project/pull/147960