update makefile.arch, factor out cmssw

[aminnj]

• updates Makefile.arch from ROOT to have latest M1 clang flags: https://raw.githubusercontent.com/root-project/root/master/etc/Makefile.arch
• factors out PhysicsTools jetcorr so that it's included only when $CMSSW_BASE is set (try CMSSW_BASE=x make -j12 vs make -j12)
• removes MakefileCI as it is no longer needed

On M1

conda activate testenv1
conda install root
cd NanoCORE
make -j8
cd Tools/unit_tests
python tests.py