[lldb] On Windows, silence warning when building with Clang ToT

Fixes:
```
[930/2017] Building CXX object tools\lldb\unittests\Thread\CMakeFiles\ThreadTests.dir\ThreadTest.cpp.obj
C:\git\llvm-project\lldb\unittests\Thread\ThreadTest.cpp(51,23): warning: cast from 'FARPROC' (aka 'long long (*)()') to 'SetThreadDescriptionFunctionPtr' (aka 'long (*)(void *, const wchar_t *)') converts to incompatible function type [-Wcast-function-type-mismatch]
   51 |       SetThreadName = reinterpret_cast<SetThreadDescriptionFunctionPtr>(
      |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   52 |           ::GetProcAddress(hModule, "SetThreadDescription"));
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
```

Author: aganea

lldb/unittests/Thread/ThreadTest.cpp

@@ -49,7 +49,7 @@ class ThreadTest : public ::testing::Test {
     HMODULE hModule = ::LoadLibraryW(L"Kernel32.dll");
     if (hModule) {
       SetThreadName = reinterpret_cast<SetThreadDescriptionFunctionPtr>(
-          ::GetProcAddress(hModule, "SetThreadDescription"));
+          (void *)::GetProcAddress(hModule, "SetThreadDescription"));
     }
     PlatformWindows::Initialize();
 #endif