libhdt/src/util/StopWatch.cpp: add missing <cstdint> ionclude (`gcc-1…

[trofi]

…3` fix)

Without the change build on gcc-13 fails as:

src/util/StopWatch.cpp: In static member function 'static std::string StopWatch::toHuman(long long unsigned int)':
src/util/StopWatch.cpp:166:5: error: 'uint64_t' was not declared in this scope
  166 |     uint64_t tot_secs = time/1000000;
      |     ^~~~~~~~
src/util/StopWatch.cpp:36:1: note: 'uint64_t' is defined in header '<cstdint>'; did you forget to '#include <cstdint>'?
   35 | #include "StopWatch.hpp"
  +++ |+#include <cstdint>

[kamahen]

This fix is also in #275