fix(react-email): broken paths on email build output for Windows (#2475)

Co-authored-by: Gabriel Miranda <[email protected]>

Author: TyMick

.changeset/plenty-wasps-walk.md

@@ -0,0 +1,5 @@
+---
+"react-email": patch
+---
+
+Normalize Windows paths in generated Next.js config

packages/react-email/src/commands/build.ts

@@ -78,14 +78,14 @@ const setNextEnvironmentVariablesForBuild = async (
   const nextConfigContents = `
 const path = require('path');
 const emailsDirRelativePath = path.normalize('${emailsDirRelativePath}');
-const userProjectLocation = '${process.cwd()}';
+const userProjectLocation = '${process.cwd().replace(/\\/g, '/')}';
 /** @type {import('next').NextConfig} */
 module.exports = {
   env: {
     NEXT_PUBLIC_IS_BUILDING: 'true',
     EMAILS_DIR_RELATIVE_PATH: emailsDirRelativePath,
     EMAILS_DIR_ABSOLUTE_PATH: path.resolve(userProjectLocation, emailsDirRelativePath),
-    PREVIEW_SERVER_LOCATION: '${builtPreviewAppPath}',
+    PREVIEW_SERVER_LOCATION: '${builtPreviewAppPath.replace(/\\/g, '/')}',
     USER_PROJECT_LOCATION: userProjectLocation
   },
   // this is needed so that the code for building emails works properly