Motivation

Fixes

$ make check -j24
...
src/libutil/tests/hash.cc:5:10: fatal error: rapidcheck/gtest.h: No such file or directory
    5 | #include <rapidcheck/gtest.h>
      |          ^~~~~~~~~~~~~~~~~~~~
compilation terminated.
make: *** [mk/patterns.mk:3: src/libutil/tests/hash.o] Error 1

Context

Checklist for maintainers

Maintainers: tick if completed or explain if not relevant

• agreed on idea
• agreed on implementation strategy
• tests, as appropriate
  • functional tests - tests/**.sh
  • unit tests - src/*/tests
  • integration tests - tests/nixos/*
• documentation in the manual
• code and comments are self-explanatory
• commit message explains why the change was made
• new feature or incompatible change: updated release notes