[RF] Fix architecture logging RooFitDriver

[guitargeek]

• print the value of the RF_ARCH macro, not the macro name

• avoid looging same info repeatedly

[phsft-bot]

Starting build on ROOT-debian10-i386/cxx14, ROOT-performance-centos8-multicore/default, ROOT-ubuntu16/nortcxxmod, ROOT-ubuntu2004/soversion, mac1015/python3, mac11/cxx17, windows10/cxx14
How to customize builds

[phsft-bot]

Build failed on windows10/cxx14.
Running on null:C:\build\workspace\root-pullrequests-build
See console output.

Failing tests:

• projectroot.roottest.root.io.transient.base.roottest_root_io_transient_base_WriteFile
• projectroot.roottest.root.tree.cache.roottest_root_tree_cache_perfstattest_libevent_build
• projectroot.roottest.root.meta.tclass.issue-6840.roottest_root_meta_tclass_issue_6840_emulatePairs_build
• projectroot.roottest.python.function.roottest_python_function_function
• projectroot.roottest.python.ttree.roottest_python_ttree_ttree
• projectroot.roottest.root.dataframe.roottest_root_dataframe_test_chainZombieFile_WILL_FAIL
• projectroot.roottest.root.dataframe.roottest_root_dataframe_templateRecursionLimit
• projectroot.roottest.root.dataframe.roottest_root_dataframe_missingBranches_WILL_FAIL
• projectroot.roottest.root.dataframe.roottest_root_dataframe_test_snapshotNFiles
• projectroot.roottest.root.dataframe.roottest_root_dataframe_test_listFilesCtor

And 25 more

[lmoneta]

LGTM!