fix(testing): ensure cypress closes the web dev server (#21759)

packages/cypress/plugins/cypress-preset.ts

@@ -5,7 +5,7 @@ import { lstatSync } from 'fs';
 import vitePreprocessor from '../src/plugins/preprocessor-vite';
 import { NX_PLUGIN_OPTIONS } from '../src/utils/constants';
 
-import { exec } from 'child_process';
+import { spawn } from 'child_process';
 import { request as httpRequest } from 'http';
 import { request as httpsRequest } from 'https';
 
@@ -65,14 +65,19 @@ export function nxBaseCypressPreset(
 }
 
 function startWebServer(webServerCommand: string) {
-  const serverProcess = exec(webServerCommand, {
+  const serverProcess = spawn(webServerCommand, {
     cwd: workspaceRoot,
+    shell: true,
+    // Detaching the process on unix will create a process group, allowing us to kill it later
+    // Windows is fine so we leave it attached to this process
+    detached: process.platform !== 'win32',
+    stdio: 'inherit',
   });
-  serverProcess.stdout.pipe(process.stdout);
-  serverProcess.stderr.pipe(process.stderr);
 
   return () => {
-    serverProcess.kill();
+    // child.kill() does not work on linux
+    // process.kill will kill the whole process group on unix
+    process.kill(-serverProcess.pid, 'SIGKILL');
   };
 }