gradle: use java "application" plugin for the facade.

engine/build.gradle

@@ -16,9 +16,12 @@
 
 // The engine build is the primary Java project and has the primary list of dependencies
 
+plugins {
+    id "java-library"
+}
+
 // Grab all the common stuff like plugins to use, artifact repositories, code analysis config, etc
 apply from: "$rootDir/config/gradle/publish.gradle"
-apply plugin: "java-library"
 
 import groovy.json.JsonSlurper
 import org.reflections.Reflections

facades/PC/build.gradle

@@ -16,6 +16,10 @@
 
 // The PC facade is responsible for the primary distribution - a plain Java application runnable on PCs
 
+plugins {
+    id "application"
+}
+
 // Grab all the common stuff like plugins to use, artifact repositories, code analysis config
 apply from: "$rootDir/config/gradle/publish.gradle"
 
@@ -70,6 +74,10 @@ ext {
     displayVersion = versionBase
 }
 
+application {
+    mainClassName project.ext.mainClassName
+}
+
 // Adjust as the Gradle 6 upgrade changed this path a bit
 sourceSets {
     main.java.outputDir = new File("$buildDir/classes")
@@ -126,6 +134,11 @@ configurations {
     }
 }
 
+run {
+    jvmArgs "-Xmx1536m", "-XshowSettings:properties"
+    workingDir rootDir
+}
+
 task game(type:JavaExec) {
     description = "Run 'Terasology' to play the game as a standard PC application"
     group = "terasology run"