build(tunnel): update publishing setup for OSSRH deprecation

The newly added zipReleasePublication task will generate a ZIP file at tunnel/build/distributions/tunnel-$VERSION-maven.zip
that can be uploaded to https://central.sonatype.com/publishing.

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

tunnel/build.gradle.kts

@@ -1,6 +1,7 @@
 @file:Suppress("UnstableApiUsage")
 
 import org.gradle.api.tasks.testing.logging.TestLogEvent
+import org.gradle.api.tasks.bundling.Zip
 
 val pkg: String = providers.gradleProperty("wireguardPackageName").get()
 
@@ -113,16 +114,29 @@ publishing {
     }
     repositories {
         maven {
-            name = "sonatype"
-            url = uri("https://oss.sonatype.org/service/local/staging/deploy/maven2/")
-            credentials {
-                username = providers.environmentVariable("SONATYPE_USER").orNull
-                password = providers.environmentVariable("SONATYPE_PASSWORD").orNull
-            }
+            name = "SonatypeUpload"
+            setUrl(layout.buildDirectory.dir("sonatype"))
         }
     }
 }
 
+val releasePublication = publishing.publications.named("release").get() as MavenPublication
+val mavenGroupPath = releasePublication.groupId.replace('.', '/')
+val mavenArtifactId = releasePublication.artifactId
+val mavenVersion = releasePublication.version
+
+tasks.register<Zip>("zipReleasePublication") {
+    dependsOn(tasks.named("publishReleasePublicationToSonatypeUploadRepository"))
+    group = "distribution"
+    description = "Zips the release publication in Maven repository layout."
+
+    val sourceDir = layout.buildDirectory.dir("sonatype/${mavenGroupPath}/${mavenArtifactId}/${mavenVersion}")
+    from(sourceDir)
+    archiveFileName.set("${mavenArtifactId}-${mavenVersion}-maven.zip")
+    destinationDirectory.set(layout.buildDirectory.dir("distributions"))
+    into("${mavenGroupPath}/${mavenArtifactId}/${mavenVersion}")
+}
+
 signing {
     useGpgCmd()
     sign(publishing.publications)