ibus-mozc : hiragana by default

Hi,

I would need some support to enable hiragana input by default when I switch to Japanese using mozc.

This issue https://github.com/google/mozc/issues/381 indicates one needs to rebuild the entire package from source with a trivial source code modification. There is a tool to do it easily with arch linux, but building for linux normally requires docker.

I'm looking for instructions to achieve it without breaking my ibus setup or struggling for hours with docker.