fix: preserve Windows system env vars for cmd.exe to work

cmd.exe needs system environment variables to function correctly.
Instead of clearing all env vars on Windows, only clear them on Unix.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: branchseer

crates/vite_task_bin/tests/test_snapshots/main.rs

@@ -173,17 +173,21 @@ fn run_case(runtime: &Runtime, tmpdir: &AbsolutePath, fixture_path: &Path) {
             let mut e2e_outputs = String::new();
             for step in e2e.steps {
                 let mut cmd = if cfg!(windows) {
-                    // Use PowerShell on Windows for better argument handling
-                    let mut cmd = Command::new("powershell.exe");
-                    cmd.args(["-NoProfile", "-NonInteractive", "-Command"]);
+                    let mut cmd = Command::new("cmd.exe");
+                    // https://github.com/nodejs/node/blob/dbd24b165128affb7468ca42f69edaf7e0d85a9a/lib/child_process.js#L633
+                    cmd.args(["/d", "/s", "/c"]);
                     cmd
                 } else {
                     let mut cmd = Command::new("sh");
                     cmd.args(["-c"]);
                     cmd
                 };
+                // On Windows, env_clear() would break cmd.exe, so only set PATH
+                // On Unix, clear all envs for reproducibility
+                if !cfg!(windows) {
+                    cmd.env_clear();
+                }
                 cmd.arg(step.as_str())
-                    .env_clear()
                     .env("PATH", &e2e_env_path)
                     .env("NO_COLOR", "1")
                     .current_dir(e2e_stage_path.join(&e2e.cwd));