Call bsc.exe directly, when no binaryPath is set in settings

[fhammerschmidt]

This should fix #514 and also will make formatting faster (at least on windows).
Supersedes #521

I refactored the binary lookup a bit so that:

• we do not need to call existsSync twice on the same file
• the function returns the binary path itself

When no binaryPath is set, the extension will lookup and use the bsc.exe now (again).

Also the message when no binary has been found could have shown null as path. I simplified it for that case.

Edit: Fixes #530 now as well.

[cristianoc]

Added comments on how to make this simpler and more future-proof.

[cristianoc]

This looks great thanks.
Just need confirmation from Windows users that this works.

[cristianoc]

TODO: check that platformDir computation is in sync with the compiler.

[fhammerschmidt]

Not quite, in rescript-vscode the platformDir also allows for "linuxarm64", the compiler does not:
https://github.com/rescript-lang/rescript-compiler/blob/master/bsc#L6-L12
https://github.com/rescript-lang/rescript-compiler/blob/master/scripts/bin_path.js#L8-L11

Edit: Or technically also "win32arm64"? Shall I adapt it to be the same as the compiler?

[cristianoc]

In that case the compiler is a little behind and could be updated.

[fhammerschmidt]

Or is the logic in rescript-vscode correct? The compiler has no directories for win32arm64 or linuxarm64, and neither do they get built in CI?

[cristianoc]

It would be kind of future-proof, if one wants to build from source.
But does not matter much either way, as this is rarely done I guess.

[cristianoc]

Looks good to me.

[cristianoc]

I think the README already aligns with this process to find the executable, and requires no change.

[cristianoc]

Merge away any time.