Build failures on recent glibc versions

[atheriel]

Building on an Ubuntu 22.04-derived system (which has glibc 2.35) yields errors such as the following:

In file included from /usr/include/signal.h:328,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/catch/catch.hpp:7644,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/TestMain.hpp:24,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/TestMain.cpp:23:
/home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/catch/catch.hpp:10376:58: error: call to non-‘constexpr’ function ‘long int sysconf(int)’
10376 |     constexpr static std::size_t sigStackSize = 32768 >= MINSIGSTKSZ ? 32768 : MINSIGSTKSZ;
      |                                                          ^~~~~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/bits/sigstksz.h:24,
                 from /usr/include/signal.h:328,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/catch/catch.hpp:7644,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/TestMain.hpp:24,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/TestMain.cpp:23:
/usr/include/unistd.h:640:17: note: ‘long int sysconf(int)’ declared here
  640 | extern long int sysconf (int __name) __THROW;
      |                 ^~~~~~~
In file included from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/TestMain.hpp:24,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/TestMain.cpp:23:
/home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/catch/catch.hpp:10435:45: error: size of array ‘altStackMem’ is not an integral constant-expression
10435 |     char FatalConditionHandler::altStackMem[sigStackSize] = {};
      |                                             ^~~~~~~~~~~~
In file included from /usr/include/signal.h:328,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/catch/catch.hpp:7644,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/TestMain.hpp:24,
                 from /home/aaron/Work/rstudio-launcher-plugin-sdk/sdk/src/tests/TestMain.cpp:23:

This appears to be related to a change made for glibc 2.34. According to their release notes:

Add _SC_MINSIGSTKSZ and _SC_SIGSTKSZ. When _SC_SIGSTKSZ_SOURCE or
_GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ are no longer
constant on Linux. MINSIGSTKSZ is redefined to sysconf(_SC_MINSIGSTKSZ)
and SIGSTKSZ is redefined to sysconf (_SC_SIGSTKSZ).

We may have to fix this to support Ubuntu 22.04.

[atheriel]

(Note: this affects only unit tests and can be worked around with cmake -DRLPS_UNIT_TESTS_DISABLED=1 ...)