fix(util/file_lock): issue on Windows

src/util/file_lock.cpp

@@ -96,9 +96,17 @@ file_lock::file_lock(char const * fname, bool exclusive):
 file_lock::~file_lock() {
 #if !defined(LEAN_EMSCRIPTEN)
     if (m_fd != -1) {
+#if !defined(LEAN_WINDOWS)
+        /* On Windows, we cannot remove the file if it is locked. */
         std::remove(m_fname.c_str());
+#endif
         flock(m_fd, LOCK_UN);
         close(m_fd);
+#if defined(LEAN_WINDOWS)
+        /* On Windows, we (to) to remove the file after we released the lock. The operation will fail if another
+           process has a handle to it. However, this is better than always keeping all .lock files. */
+        std::remove(m_fname.c_str());
+#endif
     }
 #endif
 }