FindGaudi.cmake Update, master branch (2021.05.17.)

Made FindGaudi.cmake functional with the latest version of Gaudi master, fixing the issue described in gaudi/Gaudi#180 (closed).

In a recent change (gaudi/Gaudi!1209 (merged)) Gaudi switched to preferring to use the TBBConfig.cmake file shipped with the LCG TBB installation. Setting TBB_ROOT explicitly in FindGaudi.cmake makes sure that GaudiConfig.cmake would find TBB successfully.

mentioned in issue gaudi/Gaudi#180 (closed)

AE Build SUCCESS
Build logfiles are available at Jenkins [AE-MERGE-REQUEST-CC7 #485]

merged

mentioned in commit eea05de7