make install fails on ICONPATH-related tasks when executed by non-root

[jose-d]

There is hardcoded ICONPATH there in CMakeLists.txt, and some related commands which needs root privs.

This breaks the install process when installing into PREFIX without root privileges, even when user has rights to write into PREFIX.

As I build cadabra2 using EasyBuild, for now I did workaround patch: https://github.com/jose-d/ceico-easyconfigs/blob/master/cadabra-2.2.4-foss-2018b_move_icondir.patch

But perhaps this deserves some systematical fix.

[kpeeters]

Commit b354300 should fix this. You need to run update-cache otherwise icons will not show, so I have not used that part of your patch.