Relax privateness for GCC < 13 as well

Signed-off-by: Julien Jerphanion <git@jjerphan.xyz>

include/sparrow/iterator.hpp

@@ -121,7 +121,8 @@ namespace sparrow
  it.advance(n);
  }
 
-#if _WIN32 // Workaround for access issue with msvc, when friend is involved
+// On MSVC and GCC < 13, those methods need to be public to be accessible by friend functions.
+#if _WIN32 || __GNUC__ < 13
 
  public:
 
@@ -143,11 +144,14 @@ namespace sparrow
  {
  return lhs.less_than(rhs);
  }
-#if _WIN32 // Workaround for access issue with msvc, when friend is involved
+
+// On MSVC and GCC < 13, those methods need to be public to be accessible by friend functions.
+#if _WIN32 || __GNUC__ < 13
 
  private:
 
 #endif
+
  template <class Derived, class E, class T, class R, class D>
  friend class iterator_root_base;