Rethink building procedure about gazer HOT 2 OPEN

The build process has some flaws:

1. Only gazer-bmc uses GazerZ3Solver, but disabling it does not work. (update: Also, GazerVerifier is used only in gazer-bmc)
2. gazer-bmc, gazer-theta and gazer-cfa functional tests could be split to test only portion of the code.
3. GazerLLVM linkage is a heavy operation because of the big LLVM library (libraries, to be exact). This could be added at the last build stage, if I'm not mistaken.
4. Z3Solver is downloaded (or at least the version is checked online) at every make invocation, which is too heavy for an iterative build system.

I'm not too familiar with the CMake build system, I'll try play around a bit to speed up the process (mainly for the iterative building)

from gazer.

Here are the dependencies, according to CMake

from gazer.