Build: fix build dependencies when sharing symbols

When a target is linked against code provided by a symbol provider we
need to ensure

- the symbol provider is built before generating the symbol share
- the symbol share is generated before the target
- the target is linked again when the symbol provider is updated

Change-Id: I4808ca0024c875270ad0683e9709d3db97de714b
Signed-off-by: Anubhav Raina <anubhav.raina@arm.com>