Add Java vendor as an input for compile and test tasks

In the coverage phase we use different Java vendors.
Therefore, we need to track the vendor if we want to use the build cache.

gradle/compile.gradle

@@ -9,6 +9,7 @@ if (!hasProperty('java7Home')) {
 }
 
 ext.jvmForCompilation = Jvm.current()
+ext.javaVendor = System.getProperty("java.vendor", "unknown")
 
 tasks.withType(AbstractCompile) {
     options.fork = true // Always fork compilation
@@ -36,9 +37,15 @@ tasks.withType(JavaCompile) {
     // while compiling.
     options.compilerArgs = ['-Xlint:-options', '-Xlint:-path']
     options.incremental = true
+    inputs.property('javaVendor') {
+        java7Home ? 'Oracle Corporation' : javaVendor
+    }
 }
 tasks.withType(GroovyCompile) {
     options.encoding = 'utf-8'
     options.compilerArgs = ['-Xlint:-options', '-Xlint:-path']
     groovyOptions.encoding = 'utf-8'
+    inputs.property('javaVendor') {
+        javaVendor
+    }
 }

gradle/groovyProject.gradle

@@ -47,6 +47,9 @@ testTasks.all { task ->
         // enable class unloading
         task.jvmArgs '-XX:+UseConcMarkSweepGC', '-XX:+CMSClassUnloadingEnabled'
     }
+    task.inputs.property('javaVendor') {
+        javaVendor
+    }
     doFirst {
         if (isCiServer) {
             println "maxParallelForks for '$task.path' is $task.maxParallelForks"