self-host linking #4314
Description
The C++ code in src/link.cpp is not really necessary for bootstrapping the self-hosted compiler.
stage1 only needs to be able to create libstage1.a (stage1.lib on Windows) static library which then gets linked into stage2. That means linking can be self-hosted!
This depends on #4313 being implemented first.
With this issue implemented, self-hosting the drop-in C compiler feature (see #3089) will be possible.
What it means to close this issue is that stage1 will call stage2_link() with some set of parameters that does not include a list of linker arguments (the self-hosted code will figure out the set of linker arguments).
This issue is not to be confused with #1535, which is to implement a linker in Zig. For this issue, LLD is used, same as in master branch. #1535 takes this a step further and does the actual linking itself in zig code, rather than in a third party dependency.