Use compiler flag -fvisibility=hidden

Summary:
Using compiler flag -fvisibility=hidden and explicitly setting visibility to default to public methods

#Changelog:
[Internal] [Yoga] Use compiler flag -fvisibility=hidden for reducing yoga binary size

Reviewed By: astreet

Differential Revision: D18029030

fbshipit-source-id: 545e73f9c25f3108fc9d9bb7f08c157dbc8da005

java/BUCK

@@ -25,6 +25,7 @@ yoga_cxx_library(
     compiler_flags = [
         "-fno-omit-frame-pointer",
         "-fexceptions",
+        "-fvisibility=hidden",
         "-fPIC",
         "-Wall",
         "-Werror",

java/CMakeLists.txt

@@ -24,6 +24,7 @@ add_subdirectory(${yogacore_DIR} ${yogacore_build_DIR})
 add_compile_options(
     -fno-omit-frame-pointer
     -fexceptions
+    -fvisibility=hidden
     -Wall
     -std=c++11)
 

java/jni/corefunctions.cpp

@@ -42,7 +42,8 @@ jint ensureInitialized(JNIEnv** env, JavaVM* vm) {
   return JNI_VERSION_1_6;
 }
 
-JNIEnv* getCurrentEnv() {
+// TODO why we need JNIEXPORT for getCurrentEnv ?
+JNIEXPORT JNIEnv* getCurrentEnv() {
   JNIEnv* env;
   jint ret = globalVm->GetEnv((void**) &env, JNI_VERSION_1_6);
   if (ret != JNI_OK) {