meson: do not use cairo/valgrind if disabled

-Dcairo-tests=false currently results into enabling cairo support if it
was found. Same for valgrind.

v2:
* Use underscore-prefixed variables to not change type of variable
* Use empty array for "fake" dependency instead of real empty object

v3:
* Fix typo

Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Signed-off-by: Igor Gnatenko <ignatenko@redhat.com>
1 file changed