(toolchain): Toolchain names must not be empty

[kinnison]

This fixes a problem where if you did toolchain link "" ...
then the toolchains dir was broken.

This fixes #2982

Signed-off-by: Daniel Silverstone dsilvers@digital-scurf.org

[Rustin170506]

Looks good to me!

[asomers]

This actually broke CI for Nix. Basically, we had some tasks doing rustup toolchain install +$TOOLCHAIN; cargo +$TOOLCHAIN ..., while other tasks relied on the default toolchain that was included in the Docker image. Those tasks left TOOLCHAIN blank, and did cargo +"" .... I guess we can't do that anymore.

[Rustin170506]

rustup toolchain install +$TOOLCHAIN;

Is this a typo? Because I think rustup toolchain install +1.70.0 should not work at all.

[Rustin170506]

Those tasks left TOOLCHAIN blank, and did cargo +"" .... I guess we can't do that anymore.

If it is always blank, how about removing it and using cargo ....

[asomers]

Is this a typo? Because I think rustup toolchain install +1.70.0 should not work at all.

Yes, that's right. I mean rustup toolchain install $TOOLCHAIN.

If it is always blank, how about removing it and using cargo ....

It isn't always blank, because that code is shared by multiple tasks. I'm fixing it by ensuring that each task only installs a single toolchain, so I won't need to specify a toolchain with cargo.