Fix fast API call for MinGW-w64

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
===================================================================
--- src/x64/stub-cache-x64.cc	(revision 11246)
+++ src/x64/stub-cache-x64.cc	(working copy)
@@ -477,7 +477,9 @@
   // Prepare arguments.
   __ lea(rbx, Operand(rsp, 3 * kPointerSize));
 
-#ifdef _WIN64
+#if defined(__MINGW64__)
+  Register arguments_arg = rcx;
+#elif defined(_WIN64)
   // Win64 uses first register--rcx--for returned value.
   Register arguments_arg = rdx;
 #else
@@ -1007,7 +1009,10 @@
   // Save a pointer to where we pushed the arguments pointer.
   // This will be passed as the const AccessorInfo& to the C++ callback.
 
-#ifdef _WIN64
+#if defined(__MINGW64__)
+  Register accessor_info_arg = rdx;
+  Register name_arg = rcx;
+#elif defined(_WIN64)
   // Win64 uses first register--rcx--for returned value.
   Register accessor_info_arg = r8;
   Register name_arg = rdx;