Always link dependencies for external projects
Always link dependencies for external projects

Without this, dependencies specified in ROOT_LINKER_LIBRARY() get
dropped without any warning, leading to underlinking in external
projects that make use of ROOT CMake macros (including roottest).

Fixes: ROOT-9827

root-mirror/root,root-mirror/root,karies/root,karies/root,karies/root,root-mirror/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,karies/root,olifre/root,olifre/root,olifre/root,root-mirror/root,karies/root,karies/root,karies/root,olifre/root,karies/root,olifre/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root