Fix dependency list parsing in RustAsset for paths on Windows

[lmorchard]

↪️ Pull Request

Fixes #2184

When importing a Rust asset on Windows, an error like this occurs:

×  Error writing to cache: ENOENT: no such file or directory, stat 'C:\Users\lmorc\devel\rust-wasm-play\src\C'

This appears to be an issue with how RustAsset attempts to parse a deps file using ":" - which fails on Windows because ":" is a part of file paths like C:\users\...

Switching that parsing to ": " seems to address the problem.

💻 Examples

Just following the basic Rust example from the docs

🚨 Test instructions

Build the example from the docs on Windows under PowerShell (e.g. not within a WSL Ubuntu Bash shell) - no error should occur.

✔️ PR Todo

• Added/updated unit tests for this change
  • Sorry, I'm rather new to Parcel and didn't find existing unit tests for RustAsset.js to modify. But, since this was a one-character fix, I thought it would be more handy to submit the PR as-is 😟
• Filled out test instructions (In case there aren't any unit tests)
• Included links to related issues/PRs