[x86/Linux] Fix the mistmatch between gc_thread_stub and GCThreadFunction

src/gc/gc.cpp

@@ -24711,7 +24711,7 @@ void gc_heap::compact_phase (int condemned_gen_number,
 #pragma warning(push)
 #pragma warning(disable:4702) // C4702: unreachable code: gc_thread_function may not return
 #endif //_MSC_VER
-void __stdcall gc_heap::gc_thread_stub (void* arg)
+void gc_heap::gc_thread_stub (void* arg)
 {
     ClrFlsSetThreadType (ThreadType_GC);
     STRESS_LOG_RESERVE_MEM (GC_STRESSLOG_MULTIPLY);

src/gc/gcpriv.h

@@ -1224,7 +1224,7 @@ class gc_heap
     static 
     gc_heap* balance_heaps_loh (alloc_context* acontext, size_t size);
     static
-    void __stdcall gc_thread_stub (void* arg);
+    void gc_thread_stub (void* arg);
 #endif //MULTIPLE_HEAPS
 
     CObjectHeader* try_fast_alloc (size_t jsize);