32-bit code with cmake on 64-bit machine

Using ./configure it is possible to force compile ROOT for 32-bit target on 64-bit machine by calling
./configure linux
But with cmake, it is not. There is a script cmake/modules/SetUpLinux.cmake which is using uname -m to determine architecture and it is not possible to override it. Would you consider that cmake is checking first whether ROOT_ARCHITECTURE is set by user, e.g.
cmake -DROOT_ARCHITECTURE=linux
and if not, then you perform normal architecture detection?
I have this problem with 5.34/30 but 6 might be affected as well.

This is certainly a missing feature. I have added a JIRA ticket with it sft.its.cern.ch/jira/browse/ROOT-7397
Thanks for reporting.