Revert "[compiler-rt][fuzzer] SetThreadName build fix for Mingwin attempt (llvm#106902)"

This reverts commit 7c4cffd.

This commit broke compilation in environments that don't use
winpthreads.

Author: mstorsjo

compiler-rt/lib/fuzzer/FuzzerUtilWindows.cpp

@@ -239,7 +239,6 @@ size_t PageSize() {
 }
 
 void SetThreadName(std::thread &thread, const std::string &name) {
-#if !defined(__MINGW32__)
   typedef HRESULT(WINAPI * proc)(HANDLE, PCWSTR);
   HMODULE kbase = GetModuleHandleA("KernelBase.dll");
   proc ThreadNameProc = reinterpret_cast<proc>(
@@ -254,9 +253,6 @@ void SetThreadName(std::thread &thread, const std::string &name) {
       }
     }
   }
-#else
-  (void)pthread_setname_np(thread.native_handle(), name.c_str());
-#endif
 }
 
 } // namespace fuzzer