Fix build on Linux with conda-forge dependencies (gazebosim#2944)

* Do not manually add -std=c++11 to CMAKE_CXX_FLAGS
* Update RestApi.cc

Author: traversaro

CMakeLists.txt

@@ -285,9 +285,8 @@ if (MSVC)
   set(UNFILTERED_FLAGS "/EHsc")
 endif()
 
-# Visual Studio enables c++11 support by default
 if (NOT MSVC)
-  set(UNFILTERED_FLAGS "-std=c++11")
+  set(UNFILTERED_FLAGS "")
 endif()
 
 set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${VALID_CXX_FLAGS} ${UNFILTERED_FLAGS}")

plugins/rest_web/RestApi.cc

@@ -18,7 +18,7 @@
 #include <cstring>
 #include <stdlib.h>
 #include <curl/curl.h>
-#include <inttypes.h>
+#include <cinttypes>
 
 #include "RestApi.hh"