Move MicroJIT compilation threshold into MicroJIT's header

mjit.h

@@ -150,8 +150,7 @@ mjit_exec(rb_execution_context_t *ec)
     }
 
 #ifndef MJIT_HEADER
-    const int ujit_call_threashold = 10;
-    if (rb_ujit_enabled_p() && !mjit_call_p && body->total_calls == ujit_call_threashold)  {
+    if (rb_ujit_enabled_p() && !mjit_call_p && body->total_calls == UJIT_CALL_THRESHOLD)  {
         rb_ujit_compile_iseq(iseq);
         return Qundef;
     }

ujit_compile.h

@@ -20,6 +20,8 @@ bool rb_ujit_enabled_p(void)
     return rb_ujit_enabled;
 }
 
+#define UJIT_CALL_THRESHOLD (10u)
+
 void rb_ujit_init(void);
 uint8_t *ujit_compile_insn(const rb_iseq_t *iseq, unsigned int insn_idx, unsigned int *next_ujit_idx);
 void rb_ujit_compile_iseq(const rb_iseq_t *iseq);