Goa: build working libraries for arm_v8a

[Duss Pirmin]

Hello Sebastian and all

After a lot of trail and error, I'm finally able to build shared 
libraries for the arm_v8a platform. My test component (wasmedge) runs 
successful on my iMX8 device :-).

It turns out, that when using gcc to link libraries the argument 
`-shared` passed by cmake seems to behave differently between x86_64 and 
arm_v8a.

In the arm_v8a case this needs to be prefixed with `-Wl,`.

I have changed share/goa/lib/build/cmake.tcl to add this to the linker 
flags for libraries on all platforms. This is somewhat redundant, and 
there might be a better solution, that I currently can't see. I'll be 
happy to improve during the code review.


Regards,
Pirmin