Enable -Wextra in C++ builds (#1294)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1294

X-link: https://github.com/facebook/react-native/pull/37383

Add -Wextra to the build, and fixup some more instances of -Wunused-parameter that it sufaces which were not automatically fixable.

Reviewed By: javache

Differential Revision: D45772846

fbshipit-source-id: 29bf71006f63161521fe5869c3a7d8bf7aae9c81

benchmark/YGBenchmark.c

@@ -17,6 +17,8 @@
 
 #define YGBENCHMARKS(BLOCK)                \
   int main(int argc, char const* argv[]) { \
+    (void) argc;                           \
+    (void) argv;                           \
     clock_t __start;                       \
     clock_t __endTimes[NUM_REPETITIONS];   \
     { BLOCK }                              \
@@ -78,9 +80,10 @@ static YGSize _measure(
     YGMeasureMode widthMode,
     float height,
     YGMeasureMode heightMode) {
+  (void) node;
   return (YGSize){
       .width = widthMode == YGMeasureModeUndefined ? 10 : width,
-      .height = heightMode == YGMeasureModeUndefined ? 10 : width,
+      .height = heightMode == YGMeasureModeUndefined ? 10 : height,
   };
 }