prmon v3.0.0 compilation problem with clang10/13

[elmsheus]

Hi,

the prmon version 3.0.0 has a compilation problem with clang10 and clamg13 - when using clang13 from asetup Athena,master,latest,clang13, the prmon compilation fails:

[..]
In file included from /afs/cern.ch/user/e/elmsheus/work/testarea/prmon/prmon/package/src/wallmon.cpp:4:
/afs/cern.ch/user/e/elmsheus/work/testarea/prmon/prmon/package/src/wallmon.h:30:22: error: private field 'start_time_clock_t' is not used [-Werror,-Wunused-private-field]
  unsigned long long start_time_clock_t, current_clock_t;
                     ^
/afs/cern.ch/user/e/elmsheus/work/testarea/prmon/prmon/package/src/wallmon.h:30:42: error: private field 'current_clock_t' is not used [-Werror,-Wunused-private-field]
  unsigned long long start_time_clock_t, current_clock_t;
                                         ^
2 errors generated.
make[2]: *** [package/CMakeFiles/prmon.dir/src/wallmon.cpp.o] Error 1
make[2]: *** Waiting for unfinished jobs....
[ 96%] Building CXX object package/CMakeFiles/prmon.dir/src/nvidiamon.cpp.o
make[1]: *** [package/CMakeFiles/prmon.dir/all] Error 2
make: *** [all] Error 2

This is also visible in the latest Athena external build logs after the upgrade to atlasexternals 2.0.123 which ships prmon 3.0.0: https://atlas-computing.web.cern.ch/atlas-computing/links/distDirectory/gitwww/MASTERWebArea/ardoc_web_areamaster64BC7AthenaOpt/ARDOC_Log_2021-12-11T2101/ardoc_externals_build.html

Cheers, Johannes