remoll uses `root-config --cflags` optimization flag even in Debug mode

[wdconinc]

Environment: (where does this bug occur, have you tried other environments)

• branch (master for latest released): develop
• revision (HEAD for most recent): HEAD
• OS or system: linux, beluga
• Special ROOT or Geant4 versions? avx2 architecture

Steps to reproduce: (give a step by step account of how to trigger the bug)

1. cmake -Bbuild -S. -DCMAKE_BUILD_TYPE=Debug

Expected Result: (what do you expect when you execute the steps above)

REMOLL_CXX_FLAGS should not include a -O flag

Actual Result: (what do you get when you execute the steps above)

REMOLL_CXX_FLAGS contains the -O flag from root-config --cflags, i.e. what ROOT was compiled with

Probably needs to filter out -O[^ ]* in root-config, similar to how -I is filterd out.