extremely slow build of guile3 sources

[Federico Bruni]

Hi folks

I'm building Frescobaldi flatpak using a more recent Sdk (for Qt6) and 
I noticed that building guile3 from sources requires hours (!).
It seems that this part of the build will never end, here's an excerpt:

wrote `srfi/srfi-31.go'
 BOOTSTRAP(stage1) GUILEC srfi/srfi-34.go
wrote `srfi/srfi-34.go'
 BOOTSTRAP(stage1) GUILEC srfi/srfi-35.go
wrote `srfi/srfi-35.go'
 BOOTSTRAP(stage1) GUILEC srfi/srfi-37.go
wrote `srfi/srfi-18.go'
 BOOTSTRAP(stage1) GUILEC srfi/srfi-38.go

Do you know how to reduce the build time?

I've looked at the build options here:
https://gitlab.com/lilypond/lilypond/-/blob/master/release/binaries/lib/dependencies.py?ref_type=heads#L760

and I'll try them, but I'm not sure if they are going to help with 
reducing the build time.

Please keep me in Cc in your replies as I'm not following this list.
Thanks
Federico