[lld] [LLD][COFF] Fix importing DllMain from import libraries (PR #146610)

[Alexandre Ganea via llvm-commits]

aganea wrote:

I opened https://github.com/llvm/llvm-project/pull/147152 to address your comments @mstorsjo.
If you'd prefer me to revert this instead, and re-open a new PR I can do that too.

https://github.com/llvm/llvm-project/pull/146610