Build fix for non-constexpr MINSIGSTKSZ

[davidmcgrew]

In /tests/test_patricia.cxx I suggest adding #define CATCH_CONFIG_NO_POSIX_SIGNALS right before #define CATCH_CONFIG_MAIN, because otherwise that test application won't build on Ubuntu 22.04.

The root cause is that the define MINSIGSTKSZ is no longer constexpr in more recent Linux systems, and this causes problems with catch, as outlined here. There may be better solutions, but this at least allows the package to build and the test to run.