Fix #115648: Crash on startup with an incompatible PYTHONPATH

Regression in [0]. PyPreConfig.use_environment was internalized to 0
but PyConfig.use_environment wasn't.

Thanks to @unwave for finding the root cause.

[0]: cafd6b519c

source/blender/python/intern/bpy_interface.cc

@@ -385,7 +385,12 @@ void BPY_python_start(bContext *C, int argc, const char **argv)
     PyStatus status;
     bool has_python_executable = false;
 
-    PyConfig_InitPythonConfig(&config);
+    if (py_use_system_env) {
+      PyConfig_InitPythonConfig(&config);
+    }
+    else {
+      PyConfig_InitIsolatedConfig(&config);
+    }
 
     /* Suppress error messages when calculating the module search path.
      * While harmless, it's noisy. */