Update build.gradle to tolerate being in a subproject

build.gradle

@@ -1,9 +1,49 @@
+import org.gradle.internal.os.OperatingSystem
+
+buildscript {
+    repositories {
+        mavenLocal()
+        gradlePluginPortal()
+        String frcYear = '2020'
+        File frcHome
+        if (OperatingSystem.current().isWindows()) {
+            String publicFolder = System.getenv('PUBLIC')
+            if (publicFolder == null) {
+                publicFolder = "C:\\Users\\Public"
+            }
+            def homeRoot = new File(publicFolder, "wpilib")
+            frcHome = new File(homeRoot, frcYear)
+        } else {
+            def userFolder = System.getProperty("user.home")
+            def homeRoot = new File(userFolder, "wpilib")
+            frcHome = new File(homeRoot, frcYear)
+        }
+        def frcHomeMaven = new File(frcHome, 'maven')
+        maven {
+            name 'frcHome'
+            url frcHomeMaven
+        }
+    }
+    dependencies {
+        classpath "edu.wpi.first.GradleRIO:edu.wpi.first.GradleRIO.gradle.plugin:2020.2.2"
+    }
+}
+
 plugins {
     id "java"
-    id "edu.wpi.first.GradleRIO"
+    id "maven-publish"
     id "eclipse"
 }
 
+def gradleRIOPluginId = 'edu.wpi.first.GradleRIO'
+final hasPlugin = project.getPlugins().hasPlugin(gradleRIOPluginId);
+if (hasPlugin) {
+    final Plugin plugin = project.getPlugins().getPlugin(gradleRIOPluginId)
+    println 'Plugin already applied - version ' + plugin.properties
+} else {
+    apply plugin: "edu.wpi.first.GradleRIO"
+}
+
 sourceCompatibility = JavaVersion.VERSION_11
 targetCompatibility = JavaVersion.VERSION_11