This is done by adding a DEFAULT_IF argument to add_qt_plugin, which accepts
if-evaluated expressions.
e.g.
add_qt_plugin(myplugin
DEFAULT_IF ${foo} STREQUAL ${bar}
...
)
so that this mechanism can be reused later if necessary.
Change-Id: I7eba9adaaa28e55a4f0f94cf206e868b990027e6
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>