fix(ci): use correct path separator in justfile for Windows

[tkolleh]

Summary

Fixes the Windows build release job failure: ToolNotFound: failed to find tool "gcc".

Root Cause

The justfile had a hardcoded path export:

export PATH := absolute_path(".lux/" + lua_version + "/build_dependencies/" + lua_version + "/bin") + ":" + env_var('PATH')

Because a pre-compiled Windows native just.exe is downloaded in the workflow, env_var('PATH') inside just returns the Windows-style MSYS2 PATH, delimited by semicolons (e.g. C:\msys64\ucrt64\bin;C:\msys64\usr\bin;...).

The justfile blindly prepended a path using a colon (:) separator. When just executed a shell command (via just --shell bash build), it passed down this corrupted PATH string (...bin:C:\msys64\ucrt64\bin;...). The underlying MSYS2 Bash and the subsequent lx executable failed to correctly parse this malformed hybrid PATH variable. As a result, the PATH got truncated, and /ucrt64/bin was lost entirely, causing lx to fail with failed to find tool "gcc".

Changes

• justfile: Dynamically adjust the path separator based on the operating system.

path_sep := if os() == "windows" { ";" } else { ":" }
export PATH := absolute_path(".lux/" + lua_version + "/build_dependencies/" + lua_version + "/bin") + path_sep + env_var('PATH')

Testing

This is a pre-existing issue. The justfile was hardcoded to use a Unix-style colon delimiter for paths without considering native Windows path construction when running just.exe.