Build failing on Fedora 44 clang

[mormj]

It seems clang in Fedora 44 is more strict

[ 18%] Building CXX object core/test/CMakeFiles/qa_ManagedSubGraph.dir/qa_ManagedSubGraph.cpp.o
../../../gnuradio4/core/test/qa_ManagedSubGraph.cpp:415:9: error: ignoring return value of function declared with 'nodiscard' attribute [-Werror,-Wunused-result]
415 | schedulerThreadHandle.get();
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
../../../gnuradio4/core/test/qa_ManagedSubGraph.cpp:469:9: error: ignoring return value of function declared with 'nodiscard' attribute [-Werror,-Wunused-result]
469 | schedulerThreadHandle.get();
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
../../../gnuradio4/core/test/qa_ManagedSubGraph.cpp:514:9: error: ignoring return value of function declared with 'nodiscard' attribute [-Werror,-Wunused-result]
514 | schedulerThreadHandle.get();
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
3 errors generated.
gmake[2]: *** [core/test/CMakeFiles/qa_ManagedSubGraph.dir/build.make:79: core/test/CMakeFiles/qa_ManagedSubGraph.dir/qa_ManagedSubGraph.cpp.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:3724: core/test/CMakeFiles/qa_ManagedSubGraph.dir/all] Error 2
gmake: *** [Makefile:166: all] Error 2
Error: Process completed with exit code 2.