fix(command-dev): ensure no orphaned child process on Windows (#3278)

`execa` defaults to `windowsHide: true`, which prevents child processes
from terminating child processes on exit [1].

Let's set `windowsHide: false` to terminate child processes properly on
exit.

[1]: sindresorhus/execa#433

src/commands/dev/index.js

@@ -61,7 +61,13 @@ const startFrameworkServer = async function ({ settings, exit }) {
   log(`${NETLIFYDEVLOG} Starting Netlify Dev with ${settings.framework || 'custom config'}`)
 
   // we use reject=false to avoid rejecting synchronously when the command doesn't exist
-  const frameworkProcess = execa.command(settings.command, { preferLocal: true, reject: false, env: settings.env })
+  const frameworkProcess = execa.command(settings.command, {
+    preferLocal: true,
+    reject: false,
+    env: settings.env,
+    // windowsHide needs to be false for child process to terminate properly on Windows
+    windowsHide: false,
+  })
   frameworkProcess.stdout.pipe(stripAnsiCc.stream()).pipe(process.stdout)
   frameworkProcess.stderr.pipe(stripAnsiCc.stream()).pipe(process.stderr)
   process.stdin.pipe(frameworkProcess.stdin)