Issue #28152: Fix -Wunreachable-code warning on clang

Replace 0 with (0) to ignore a compiler warning about dead code on
"((int)(SEM_VALUE_MAX) < 0)": SEM_VALUE_MAX is not negative on Linux.

Modules/_multiprocessing/multiprocessing.c

@@ -171,8 +171,11 @@ PyInit__multiprocessing(void)
     {
         PyObject *py_sem_value_max;
         /* Some systems define SEM_VALUE_MAX as an unsigned value that
-         * causes it to be negative when used as an int (NetBSD). */
-        if ((int)(SEM_VALUE_MAX) < 0)
+         * causes it to be negative when used as an int (NetBSD).
+         *
+         * Issue #28152: Use (0) instead of 0 to fix a warning on dead code
+         * when using clang -Wunreachable-code. */
+        if ((int)(SEM_VALUE_MAX) < (0))
             py_sem_value_max = PyLong_FromLong(INT_MAX);
         else
             py_sem_value_max = PyLong_FromLong(SEM_VALUE_MAX);