Merge branch 'bugfix/cmake-apply-compile-options-in-add-dune-all-flags' into 'master'

[cmake] Apply compile options in add_dune_all_flags()

See merge request !460 (merged)

(cherry picked from commit 75fa89c9)

556f4491 [cmake] Apply compile options in add_dune_all_flags()

mentioned in merge request dune-istl!190 (merged)

merged

mentioned in commit a8a0018c