fix gradle compliation (#925)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/925

Gradle is failing to compile yoga for two reasons:
1. Ever since `YogaNodeJNIPhantomRefs` was introduced which uses `DestructorThread.Destructor` from fbjni which was the first direct Java dependency from yoga java to fbjni java code.

2. Adding a missing gradle endpoint for `testutil` since it is now required for yoga unit-tests

Differential Revision: D17274226

fbshipit-source-id: 9a4919f1bb72ac1f52b6b32ce7acbff435d587e4

java/build.gradle

@@ -60,8 +60,10 @@ android {
 dependencies {
     compileOnly 'com.google.code.findbugs:jsr305:3.0.1'
     compileOnly project(':yoga:proguard-annotations')
+    compile project(':libfb')
     implementation 'com.facebook.soloader:soloader:0.5.1'
     testImplementation 'junit:junit:4.12'
+    testCompile project(':testutil')
 }
 
 task sourcesJar(type: Jar) {