Try to:
locate root.exe
So, first remove the offending line from your .bashrc, then start a new terminal (so that the “old” root settings are gone) and then build your new root from scratch again (i.e. delete the “test_build” and “root-6.06.08” subdirectories, unpack the source code again, …).
BTW. Add -Dall=“ON” -Dsoversion=“ON” to your cmake line.
Last, but not least … make sure that you read the notes about installing a “system default” ROOT version in a “system default” subdirectory (this applies to your “/scratch/HEPsoftware/local”, as well) : Missing Canvas