build: remove -std flag from client script

It is defined by the daemon

Change-Id: I4ee88a4a35d68f1bfe7b5e002356d4df2a5e9433

compile-ios.sh

@@ -120,7 +120,7 @@ do
         CFLAGS+=" -O3"
     fi
 
-    CXXFLAGS="-std=c++11 -stdlib=libc++ $CFLAGS"
+    CXXFLAGS="-stdlib=libc++ $CFLAGS"
     LDFLAGS="$CFLAGS"
 
 	./autogen.sh || exit 1