HHH-20341 Fix syntax of maven mirror definition

As it was, it was simply being ignored.

Author: yrodiere

MAINTAINERS.md

@@ -20,6 +20,7 @@ Continuous integration is split across two platforms:
 The Hibernate ORM build can use a mirror instead of Maven central.
 To do so, set the `MAVEN_MIRROR` environment variable to the URL of your mirror,
 e.g. `http://something-on-aws.com/path/to/repo`.
+The mirror can use unsecure HTTP, but obviously that exposes you to MITM attacks unless the build runs in a completely isolated network.
 
 ### GitHub Actions workflows
 

settings.gradle

@@ -28,7 +28,10 @@ dependencyResolutionManagement {
         // TODO Move to infra overrides instead;
         //  see https://blog.gradle.org/maven-central-mirror#overriding-the-urls-for-maven-central-and-the-plugin-portal-repositories
         if ( System.env['MAVEN_MIRROR'] ) {
-            url( System.env['MAVEN_MIRROR'] )
+            maven {
+                url System.env['MAVEN_MIRROR']
+                allowInsecureProtocol = true
+            }
         }
 
         mavenCentral()