This reverts commit 44df042c.
There was nothing to fix. We depend on using the right
branch in dune-testtools that has the additional argument.

- We do not use the other versions anyway
- Currently, if two versions are installed, even if one of them is 3.8,
sometimes the wrong one is found and the format feature is disabled

We actually need a mix of cmake magic and config.h to work
* if alberta is not used (then the config.h define is taken)
* alberta is actually used (then the dimension has to be specified for the
  target at hand with add_dune_alberta_flags(GRIDDIM $dim $target))

Previously, TBB_INCLUDE_DIR was ignored, although documented as possible
hint to where the tbb include might be. No it is respected, hopefully
without breaking findidn of system installation ...

The old behavior only added `-lboost_system` but did not add
`-L/path/to/boost/lib`.

Previously, TBB_INCLUDE_DIR was ignored, although documented as possible
hint to where the tbb include might be. No it is respected, hopefully
without breaking findidn of system installation ...

The old behavior only added `-lboost_system` but did not add
`-L/path/to/boost/lib`.

reduces spurious re-runs by only updatin gthe builder defition
when it actually changed