Build: Allow for local file based deploy

Allow run of `gradle uploadArchives` if the endpoint is local
and file based, otherwise reject so we dont accidentally push
into sonatype or sth.

This is the sister PR to elastic/elasticsearchelastic/elasticsearch#17399

Original commit: elastic/x-pack-elasticsearch@9704b8ea9a

build.gradle

@@ -5,7 +5,7 @@ if (project.projectDir.name != 'x-plugins') {
 subprojects {
   // we must not publish to sonatype until we have set up x-plugins to only publish the parts we want to publish!
   project.afterEvaluate {
-    if (project.plugins.hasPlugin('com.bmuschko.nexus')) {
+    if (project.plugins.hasPlugin('com.bmuschko.nexus') && project.nexus.repositoryUrl.startsWith('file://') == false) {
       install.enabled = false
       uploadArchives.enabled = false
     }