CheckVariableExists

Check if the variable exists.

CHECK_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_LINK_OPTIONS

New in version 3.14: list of options to pass to link command.

CMAKE_REQUIRED_LIBRARIES

list of libraries to link.

CMAKE_REQUIRED_QUIET

New in version 3.1: execute quietly without messages.