Gradle wrapper not created on windows

Uses gradle.bat vs gradle on windows.
Changed Error to Warn when gradle not found.

Fixes quarkusio#4745

devtools/maven/src/main/java/io/quarkus/maven/CreateProjectMojo.java

@@ -18,6 +18,7 @@
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
@@ -58,6 +59,8 @@
 @Mojo(name = "create", requiresProject = false)
 public class CreateProjectMojo extends AbstractMojo {
 
+    final private static boolean IS_WINDOWS = System.getProperty("os.name").toLowerCase(Locale.ROOT).contains("windows");
+
     private static String pluginKey;
 
     public static String getPluginKey() {
@@ -216,15 +219,16 @@ public void execute() throws MojoExecutionException {
 
     private void createGradleWrapper(File projectDirectory) {
         try {
-            ProcessBuilder pb = new ProcessBuilder("gradle", "wrapper",
+            String gradleName = IS_WINDOWS ? "gradle.bat" : "gradle";
+            ProcessBuilder pb = new ProcessBuilder(gradleName, "wrapper",
                     "--gradle-version=" + MojoUtils.getGradleWrapperVersion()).directory(projectDirectory)
                             .inheritIO();
             Process x = pb.start();
 
             x.waitFor();
 
             if (x.exitValue() != 0) {
-                getLog().error("Unable to install the Gradle wrapper (./gradlew) in project. See log for details.");
+                getLog().warn("Unable to install the Gradle wrapper (./gradlew) in project. See log for details.");
             }
 
         } catch (InterruptedException | IOException e) {