Don't apply spotless plugin to test-platform subproject

Author: emlun

build.gradle

@@ -62,7 +62,6 @@ allprojects {
   ext.dirtyMarker = "-DIRTY"
 
   apply plugin: 'com.cinnober.gradle.semver-git'
-  apply plugin: 'com.diffplug.spotless'
   apply plugin: 'idea'
 
   group = 'com.yubico'
@@ -91,12 +90,15 @@ subprojects {
     mavenCentral()
   }
 
-  spotless {
-    java {
-      googleJavaFormat()
-    }
-    scala {
-      scalafmt('2.6.3').configFile(rootProject.file('scalafmt.conf'))
+  if (project !== project(':test-platform')) {
+    apply plugin: 'com.diffplug.spotless'
+    spotless {
+      java {
+        googleJavaFormat()
+      }
+      scala {
+        scalafmt('2.6.3').configFile(rootProject.file('scalafmt.conf'))
+      }
     }
   }
 }