unset

Unset a variable, cache variable, or environment variable.

unset(<variable> [CACHE | PARENT_SCOPE])

Removes the specified variable causing it to become undefined. If CACHE is present then the variable is removed from the cache instead of the current scope.

If PARENT_SCOPE is present then the variable is removed from the scope above the current scope. See the same option in the set() command for further details.

<variable> can be an environment variable such as:

unset(ENV{LD_LIBRARY_PATH})

in which case the variable will be removed from the current environment.