Remember compiler options during attach.

Note:
- Move compiler options into `mjsCompiler` struct.
- The compiler options from the attached model are not written by mj_SaveXML.
PiperOrigin-RevId: 689391440
Change-Id: I1d63c146a32f87c737b7a55b64a54b0ffe3aecc9

python/mujoco/codegen/generate_spec_bindings.py

@@ -39,8 +39,12 @@ def _value_binding_code(
     fullvarname = 'ptr->' + varname
   if field.name.startswith('mjs'):  # all other mjs are raw structs
     fulltype = field.name.replace('mjs', 'raw::Mjs')
-    if field.name == 'mjsPlugin' or field.name == 'mjsOrientation':
-      fulltype = fulltype + '&'  # plugin and orientation are not pointers
+    if (
+        field.name == 'mjsPlugin'
+        or field.name == 'mjsOrientation'
+        or field.name == 'mjsCompiler'
+    ):
+      fulltype = fulltype + '&'  # plugin, orientation, compiler are not pointers
     else:
       fulltype = fulltype + '*'
   # non-mjs structs