Default CMake builds

[ppenzin]

On platforms on which ChacoreCore builds via CMake allow the canonical CMake workflow. In the most basic case it would be something like this (ninja generator should be enabled as well):

$ cd build
$ cmake /path/to/ChakraCore/
$ make

• (Basic workflow)

Extra credit:

• testing support
• expose more configuration options to the command line cmake invocation
  • ICU embedding
• Windows support

Windows support may be too ambitious of a goal at the moment, but projects using CMake (which we expect might embed ChakraCore) often build on Windows as well, and we should not completely rule that out.