rust: copy std dll into /usr/bin

[ognevny]

fixes #5784

[Berrysoft]

Should it be a link?

[ognevny]

I believe that for windows-gnu it's a copied file, but didn't check rust sources

[Berrysoft]

Oh, yes. It's a copied one.

[500-internal-server-error]

Probably a good idea to hardlink it, so as not to waste space.

[oech3]

conflicting

[ognevny]

I know, I don't actually like this approach

[oech3]

any response from upstream?

[ognevny]

I don't know. I didn't open any issue in rust repo, because -Cprefer-dynamic is not recommended to use

[500-internal-server-error]

Upstream doesn't guarantee anything outside $prefix/rustlib, so we should merge this.

[oech3]

How many binaries linked against it?

[500-internal-server-error]

Not many I imagine, even the one case I hit it was only in the test suite, not the build. Still would be nice not to hit it, though.

[Berrysoft]

Almost all rust binaries link std statically. It would be possible to link std dynamically if the std dll is in /usr/bin, but it would be massive for packagers, because every time the rust package updates, they need to update all binaries compiled by rust.

However, the proc macros use the std dll. cargo and rustc are responsible for their environments and the std dll doesn't have to be inside /usr/bin. Only some corner cases, like a test suite for some proc macro libs, might need the std dll in PATH.