Fix test util to measure text properly based on flex direction (#1768)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1768

Depending on the flex direction text will either be capped to the measured size or to the longest word, so I added that functionality

Reviewed By: mlord93

Differential Revision: D67106199

fbshipit-source-id: 0b4691768809004043a847f3fc5f7b94e92f1575

gentest/gentest-cpp.js

@@ -502,7 +502,7 @@ CPPEmitter.prototype = Object.create(Emitter.prototype, {
   },
 
   YGNodeSetMeasureFunc: {
-    value: function (nodeName, innerText) {
+    value: function (nodeName, innerText, _) {
       this.push(`YGNodeSetContext(${nodeName}, (void*)"${innerText}");`);
       this.push(
         `YGNodeSetMeasureFunc(${nodeName}, &facebook::yoga::test::IntrinsicSizeMeasure);`,