make user library compilation optional

We need some CMAKEList options to make it optional (as it implies some asm code in ARM for example)

Changes are on !216 (Should be moved to main)

marked this issue as related to #331 (closed)

created branch rnou/330-make-user-library-compilation-optional to address this issue

mentioned in merge request !219 (merged)

mentioned in commit 33087b8f

closed with merge request !219 (merged)