better error message if toolchain specified in Anchor.toml isn't installed

[jim4067]

When running solana 1.18.8 and I specify 1.18.20 in the toolchain section of my Anchor.toml, it errors out with this cryptic message

thread 'main' panicked at cli/src/lib.rs:545:18:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

It would be better if an error message like specifid toochain unavailable locally and give the user the option to install it

[acheroncrypto]

This should already work if you specify the version correctly (without spaces or unsupported characters). Can you show the [toolchain] section of your Anchor.toml?

[jim4067]

Can you show the [toolchain] section of your Anchor.toml

[toolchain]
anchor_version = "0.30.1"  
solana_version = "1.18.20"  

steps to reproduce.

1. switch to 1.18.8
2. try running anchor build

[acheroncrypto]

The issue is solana-install >1.18.19 logs:

⚠️  solana-install is deprecated and will be discontinued when v1.18 is no longer supported. Please switch to Agave: https://github.com/anza-xyz/agave/wiki/Agave-Transition

solana-labs/solana@526b7fa

which makes parsing the version fail.

We'll migrate to the new one for the next version, but you can use any version before 1.18.19 (1.18.17 is recommended).