Add missing utility header for std::move (#2572)

Found via clang-tidy.

src/s3fs.cpp

@@ -28,6 +28,7 @@
 #include <mutex>
 #include <set>
 #include <unistd.h>
+#include <utility>
 #include <dirent.h>
 #include <sys/types.h>
 #include <sys/wait.h>