libuv: Suppress conversion warning on Windows

Add a cast to avoid the conversion warning with minimal changes to
third-party code.

Utilities/cmlibuv/src/win/fs.c

@@ -1243,7 +1243,7 @@ void fs__mktemp(uv_fs_t* req, uv__fs_mktemp_func func) {
   uint64_t v;
   char* path;
   
-  path = req->path;
+  path = (char*)req->path;
   len = wcslen(req->file.pathw);
   ep = req->file.pathw + len;
   if (len < num_x || wcsncmp(ep - num_x, L"XXXXXX", num_x)) {