test/QIR-static: Consider generating the _library_ rather than _executable_

[kuzminrobin]

Consider generating the library from the .qs files rather than executable (in order to avoid cheating the compiler by "calling" from Test_Arrays() the unrelated functions)
See details here.

[IrinaYatsenko]

We do need a test for the generated C-compatible entry points, and rather than having it as a separate Q# project and a separate test binary to do that, I'd wait for the multiple entry points to be supported and just go back to marking all of the test functions as entry points inside the same project...