Document Zig's built-in linker options

[jepotter1-archive]

This PR adds documentation for the ld.lld, lld-link, and wasm-ld options, which are currently exposed but not documented.

Note that I haven't tested this locally but it should work fine regardless since it only adds a few lines to the help string.

[g-w1]

Why not just use zig ld? I think these are only supposed to be used internally.

[jepotter1-archive]

Why not just use zig ld? I think these are only supposed to be used internally.

@g-w1 error: unknown command: ld

This is on Zig 0.8.0.

[g-w1]

Ah, sorry, I meant, build-exe or build-lib, or build-obj. You can just pass the things you would like to link to args as to those programs.

[jepotter1-archive]

Ah, sorry, I meant, build-exe or build-lib, or build-obj. You can just pass the things you would like to link to args as to those programs.

Is build-lib a drop-in LD though?

Like, can I set LD=zig build-lib?

[g-w1]

I do not think so, but also see #8755.

[jepotter1-archive]

The use case here is that I'm making a Linux distribution and a lot of build scripts (e.g. Autotools, CMake) automatically use the system linker rather than Zig's linker. I can override this by setting LD to something... which I'm currently setting to zig ld.lld and it seems to work.

[jepotter1-archive]

The problem is I had to do a lot of digging to find this information (including reading your IRC messages in the IRC log). I'm just submitting this patch so maybe the next person who is crazy enough to try to make a Linux distro based on Zig will have it slightly easier 😅

[g-w1]

I think this is a workaround, it might not be that hard to just implement #8755 depending on the target os (may be a bit harder to hook up the self-hosted linker backends, but for linux, it should just be forwarding the args to argv[0] ld.lld.)
(ps. linux distro based on zig is pretty cool)

[alexrp]

I think it's going to be a long while still until zig ld can replace LLD on all target platforms. Wouldn't it make sense to document these until then? The command line interface isn't set in stone until 1.x anyway.

[g-w1]

Zig ld != self-hosted linker. You can still shell out to ld.lld in zig ld (as I said).

[alexrp]

Oh, sorry, I misunderstood your earlier comments.

Are we sure that a single zig ld interface covers all command line options people might want to use? ld.lld and lld-link have radically different CLIs after all.

[g-w1]

From the issue:

some projects may want to use Zig as a drop-in replacement for other linkers.

[andrewrk]

These are internal, intentionally not part of the publicly documented CLI. Please see #8755