Provide a boolean option that the user can optionally select.
option(<variable> "<help_text>" [value])
If no initial
<value> is provided, boolean
OFF is the default value.
<variable> is already set as a normal or cache variable,
then the command does nothing (see policy
For options that depend on the values of other options, see
the module help for
In CMake project mode, a boolean cache variable is created with the option value. In CMake script mode, a boolean variable is set with the option value.