Use boost::has_trivial_copy_constructor rather than std.

Summary:
- libc++ doesn't ship with this method defined. Just use Boost's version
of this instead.

Test Plan:
- fbconfig -r folly && fbmake runtests
- ./configure && make check on Ubuntu/FC/Mac

Reviewed By: meyering@fb.com

FB internal diff: D998593

diff --git a/folly/FBVector.h b/folly/FBVector.h
index e1319587727099bcad85ec531249d57a8599da0f..db7ee4f1c0ed18196188335a41f7e36858536ecd 100644 (file)
--- a/folly/FBVector.h
+++ b/folly/FBVector.h
@@ -316,7 +316,7 @@ public:
 private:
 
   typedef std::integral_constant<bool,
-      std::has_trivial_copy_constructor<T>::value &&
+      boost::has_trivial_copy_constructor<T>::value &&
       sizeof(T) <= 16 // don't force large structures to be passed by value
     > should_pass_by_value;
   typedef typename std::conditional<