# CheckVariableExists

Check if the variable exists.

    CHECK_VARIABLE_EXISTS(VAR VARIABLE)

    VAR      - the name of the variable
    VARIABLE - variable to store the result
               Will be created as an internal cache variable.

This macro is only for C variables.

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_LIBRARIES = list of libraries to link
    CMAKE_REQUIRED_QUIET = execute quietly without messages