Move Gradle build logic to a setup hook

nix/init.gradle

@@ -0,0 +1,42 @@
+import org.gradle.util.GradleVersion
+
+static boolean versionAtLeast(String version) {
+    return GradleVersion.current() >= GradleVersion.version(version)
+}
+
+static void configureRepos(RepositoryHandler repositories) {
+    repositories.configureEach { ArtifactRepository repo ->
+        if (repo instanceof MavenArtifactRepository) {
+            repo.setArtifactUrls(new HashSet<URI>())
+            repo.url 'file:@mavenRepo@'
+            repo.metadataSources {
+                gradleMetadata()
+                mavenPom()
+                artifact()
+            }
+        } else if (repo instanceof IvyArtifactRepository) {
+            repo.url 'file:@mavenRepo@'
+            repo.layout('maven')
+            repo.metadataSources {
+                gradleMetadata()
+                ivyDescriptor()
+                artifact()
+            }
+        } else if (repo instanceof UrlArtifactRepository) {
+            repo.url 'file:/homeless-shelter'
+        }
+    }
+}
+
+beforeSettings { settings ->
+    configureRepos(settings.pluginManagement.repositories)
+    configureRepos(settings.buildscript.repositories)
+    if (versionAtLeast("6.8")) {
+        configureRepos(settings.dependencyResolutionManagement.repositories)
+    }
+}
+
+beforeProject { project ->
+    configureRepos(project.buildscript.repositories)
+    configureRepos(project.repositories)
+}