Draft: CMakeLists.txt: fix parallel compilation

This is a branch of what we presented today on compiling globo with CMake. Feel free to comment.

Below are the compilation times first compilation:

[...]
[100%] Built target globo_cpld

real	0m55.887s
user	2m19.961s
sys	1m39.691s

compilation without modifications:

[100%] Built target globo_cpld

real	0m3.453s
user	0m2.377s
sys	0m3.750s

The templated build system rebuilds everything every time (unless you modify manually the boolean in the header of scripts/utils/globo_compile_all.sh):

real	4m33.552s
user	4m0.889s
sys	0m23.440s