[Object] Use COFF archive format for import libraries.

This is similar to D143540 for import libraries. ARM64EC will need it
for EC symbol table, but it should be fine for other targets as well
and it improves MSVC compatibility. I left mingw case unchanged to be
safe, although I think that it wouldn't hurt to change that as well.

The visible effect in tests is a sorted symbol map.

Revieved By: mstorsjo
Differential Revision: https://reviews.llvm.org/D156473