[ ] create examples.
[x] finish simple cjit compiler, pass sanity test. [x] use more directories structure, add cmake support. (cjit/c-jit.hh cjit/c-jit.cc utest/xxx.cc) [x] add "third-part/" folder for mir or maybe LLVM backend. [x] import and use utest in test system. [x] add first 2-3 test cases.