Revive free-threaded build to be built.

Author: corona10

Include/internal/pycore_stackref.h

@@ -464,6 +464,12 @@ PyStackRef_CLOSE_SPECIALIZED(_PyStackRef ref, destructor destruct)
     PyStackRef_CLOSE(ref);
 }
 
+static inline int
+PyStackRef_RefcountOnObject(_PyStackRef ref)
+{
+    return (ref.bits & Py_TAG_REFCNT) == 0;
+}
+
 static inline _PyStackRef
 PyStackRef_DUP(_PyStackRef stackref)
 {

Python/optimizer.c

@@ -119,6 +119,7 @@ _PyOptimizer_Optimize(
     PyInterpreterState *interp = _PyInterpreterState_GET();
     assert(interp->jit);
     assert(!interp->compiling);
+#ifndef Py_GIL_DISABLED
     interp->compiling = true;
     // The first executor in a chain and the MAX_CHAIN_DEPTH'th executor *must*
     // make progress in order to avoid infinite loops or excessively-long
@@ -160,6 +161,9 @@ _PyOptimizer_Optimize(
     assert((*executor_ptr)->vm_data.valid);
     interp->compiling = false;
     return 1;
+#else
+    return 0;
+#endif
 }
 
 static _PyExecutorObject *

configure

@@ -2799,7 +2799,7 @@ AC_MSG_RESULT([$tier2_flags $jit_flags])
 if test "$disable_gil" = "yes" -a "$enable_experimental_jit" != "no"; then
   # GH-133171: This configuration builds the JIT but never actually uses it,
   # which is surprising (and strictly worse than not building it at all):
-  AC_MSG_ERROR([--enable-experimental-jit cannot be used with --disable-gil.])
+  AC_MSG_WARN([--enable-experimental-jit does not work correctly with --disable-gil.])
 fi
 
 case "$ac_cv_cc_name" in