pkgsCross.mingw32.gcc11Stdenv: update mcfgthread patches for gcc-11

Without the change mingw32-gcc fails to build as:

In file included from /build/gcc-11.2.0/libstdc++-v3/libsupc++/cxxabi.h:49,
from ../../../../gcc-11.2.0/libstdc++-v3/libsupc++/atexit_thread.cc:24:
../../../../gcc-11.2.0/libstdc++-v3/libsupc++/atexit_thread.cc:36:3: error: 'int __cxxabiv1::__cxa_thread_atexit(void (*)(void*), void*, void*)' should have been declared inside '__cxxabiv1'
36 | _GLIBCXX_NOTHROW
| ^~~~~~~~~~~~~~~~
../../../../gcc-11.2.0/libstdc++-v3/libsupc++/atexit_thread.cc:34:1: error: conflicting declaration of C function 'int __cxxabiv1::__cxa_thread_atexit(void (*)(void*), void*, void*)'
34 | __cxxabiv1::__cxa_thread_atexit (void (*dtor)(void *),
| ^~~~~~~~~~

The change follows upstream change introduced in
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=7fc0f78c3f43af1967cb7b1ee8f4947f3b890aa2

pkgs/development/compilers/gcc/11/Added-mcf-thread-model-support-from-mcfgthread.patch

···
 +#ifdef __USING_MCFGTHREAD__
 +
 +#include <mcfgthread/gthread.h>
-+
++namespace __cxxabiv1 {
 +extern "C" int
-+__cxxabiv1::__cxa_thread_atexit (void (*dtor)(void *),
++__cxa_thread_atexit (void (_GLIBCXX_CDTOR_CALLABI *dtor)(void *),
 +				 void *obj, void *dso_handle)
 +  _GLIBCXX_NOTHROW
 +{
 +  return ::_MCFCRT_AtThreadExit((void (*)(_MCFCRT_STD intptr_t))dtor, (_MCFCRT_STD intptr_t)obj) ? 0 : -1;
 +  (void)dso_handle;
 +}
-+
++}
 +#else // __USING_MCFGTHREAD__
 +
  #ifdef _GLIBCXX_THREAD_ATEXIT_WIN32