fix(port): add missing #include

Fix the following build error on newer Ubuntu:

```
src/quick-lint-js/port/thread-name.cpp:41:55: error: ‘uintptr_t’ in namespace ‘std’ does not name a type
   41 |   int rc = ::prctl(PR_SET_NAME, reinterpret_cast<std::uintptr_t>(new_name_cstr),
      |                                                       ^~~~~~~~~
```

Author: strager

src/quick-lint-js/port/thread-name.cpp

@@ -2,6 +2,7 @@
 // See end of file for extended copyright information.
 
 #include <cerrno>
+#include <cstdint>
 #include <cstring>
 #include <quick-lint-js/assert.h>
 #include <quick-lint-js/logging/log.h>