Eliminates std::filesystem usage in utils.cc (#1346)

Depends on gazebosim/gz-common#312

See gazebo-tooling/release-tools#639

Basically, this removes the dependency on `std::filesystem` in  ign-gazebo as its been causing issues when binaries are produced by diffrent compiler versions. This current version makes sure that we keep all `std::filesystem` code in` ign-common`.

Signed-off-by: Arjo Chakravarty <arjo@openrobotics.org>

Co-authored-by: Louise Poubel <louise@openrobotics.org>

src/Util.cc

@@ -15,21 +15,6 @@
  *
 */
 
-#ifndef __APPLE__
-  #if (defined(_MSVC_LANG))
-    #if (_MSVC_LANG >= 201703L || __cplusplus >= 201703L)
-      #include <filesystem>  // c++17
-    #else
-      #define _SILENCE_EXPERIMENTAL_FILESYSTEM_DEPRECATION_WARNING
-      #include <experimental/filesystem>
-    #endif
-  #elif __GNUC__ < 8
-    #include <experimental/filesystem>
-  #else
-    #include <filesystem>
-  #endif
-#endif
-
 #include <ignition/common/Filesystem.hh>
 #include <ignition/common/StringUtils.hh>
 #include <ignition/common/Util.hh>
@@ -349,20 +334,8 @@ std::string asFullPath(const std::string &_uri, const std::string &_filePath)
     return _uri;
   }
 #else
-  // Not a relative path, return unmodified
-  #if (defined(_MSVC_LANG))
-    #if (_MSVC_LANG >= 201703L || __cplusplus >= 201703L)
-      using namespace std::filesystem;
-    #else
-      using namespace std::experimental::filesystem;
-    #endif
-  #elif __GNUC__ < 8
-    using namespace std::experimental::filesystem;
-  #else
-    using namespace std::filesystem;
-  #endif
   if (_uri.find("://") != std::string::npos ||
-      !path(_uri).is_relative())
+      !common::isRelativePath(_uri))
   {
     return _uri;
   }