Check if the given C++ source code compiles and runs.


<code>   - source code to try to compile
<var>    - variable to store the result
           (1 for success, empty for failure)
           Will be created as an internal cache variable.

The following variables may be set before calling this macro to modify the way the check is run:

CMAKE_REQUIRED_FLAGS = string of compile command line flags
CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
CMAKE_REQUIRED_INCLUDES = list of include directories
CMAKE_REQUIRED_LIBRARIES = list of libraries to link
CMAKE_REQUIRED_QUIET = execute quietly without messages