package architectures not compatible with system arch

[mauro at freedomotic.com]

Hi all,
I created a package without specifying in package.yaml. So it considers
"all" as architecture.
I installed it on Raspi2 without problems.
Now I added a java jre and tried to install on Udoo board (armhf).
In this case I received
"cannot install ..snap Package architectures "all" not compatible
withsystem architecture "armhf".

Is a problem related to java or not? No message about java.
I found on google a way to force the installation with the option
--force-architecture. But this is not recognized by snappy.

Thanks
Mauro