Redesign how linking in Rust works

[brson]

Right now it's very ad-hoc, with users specifying link_args of unspecified format, tied to C compiler implementation, propogating linker arguments between crates. It's a mess. If we don't fix this we're going to end up tied to arbitrary, platform-specific C compiler semantics. Rust should have some sort of linker model baked in that just works for most common cases.

[brson]

Nominating.

[brson]

This is mostly about linking to native libraries.

[catamorphism]

1.0, high

[Aatch]

I would like to add my support for this. While the most common cases, like building simple executables or shared libraries, are reasonably well-handled by rustc right now, anything outside of that is hell to get right.

I'd like to have much more control over the compilation of rust code right now, as the uncommon cases are very difficult to get right. This is important for embedded environments and similar places.

[alexcrichton]

Closed by #10528