Improve error message when platform specified by absolute path

[YanniPapandreou]

Description

Closes #8549.

As described in the above issue when running the roc compiler on a main.roc with a platform specified as an absolute file path:

app [main!] { pf: platform "/Users/yanni/projects/roc-platform-template-zig/platform/main.roc" }

import pf.Stdout
import pf.Stdin

main! = |_args| {
    Stdout.line!("What's your name?")
    name = Stdin.line!()
    Stdout.line!("Hello, ${name}!")
    Ok({})
}

I obtained the following error:

$ ./zig-out/bin/roc --no-cache main.roc
error: No platform found. Every Roc app requires a platform.
error: Failed to set up shared memory with ModuleEnv: error.NoPlatformFound

With this PR I know get this error message, indicating that absolute paths are not allowed:

error: No platform found. Absolute paths are not allowed for platform specification: "/Users/yanni/projects/roc-platform-template-zig/platform/main.roc"
error: Failed to set up shared memory with ModuleEnv: error.NoPlatformFound

Checks

• I've build and tested the roc compiler on the program above.
• I've run the tests with zig build snapshot && zig build test and they all passed.

[Anton-4]

Thanks for contributing @YanniPapandreou :)
Could you add a tip as well stating that people should instead use relative paths like ../platform or a URL?

[YanniPapandreou]

Thanks for contributing @YanniPapandreou :) Could you add a tip as well stating that people should instead use relative paths like ../platform or a URL?

Sure would something like this be better - I've pushed a change. Here is the error message now:

error: No platform found. Absolute paths are not allowed for platform specification: "/Users/yanni/projects/roc-platform-template-zig/platform/main.roc". Please use a relative path like `./path/to/platform` or a URL.
error: Failed to set up shared memory with ModuleEnv: error.NoPlatformFound

On smaller terminals it wraps to the next line as shown in picture below: