Enhance init_includes to handle dynamic include paths

src/xinterpreter.cpp

@@ -357,7 +357,25 @@ __get_cxx_version ()
 
     void interpreter::init_includes()
     {
+        // Add the standard include path
         Cpp::AddIncludePath((xeus::prefix_path() + "/include/").c_str());
+
+        // Add non-standard include paths from XEUS_SEARCH_PATH
+        const char* non_standard_paths = XEUS_SEARCH_PATH;
+
+        if (non_standard_paths && std::strlen(non_standard_paths) > 0)
+        {
+            // Split the paths by colon ':' and add each one
+            std::istringstream stream(non_standard_paths);
+            std::string path;
+            while (std::getline(stream, path, ':'))
+            {
+                if (!path.empty())
+                {
+                    Cpp::AddIncludePath(path.c_str());
+                }
+            }
+        }
     }
 
     void interpreter::init_preamble()