It must be because of my rust configuration but it compiled correctly and I disabled Jonathon's handy.patch, sorry. Now it should compile without problem.
Libhandy is not necessary to compile it, as it is downloaded from the source branch, just like many other packages. Libhandy0 was necessary for its execution and until now I had not realized it because by default it is installed by other packages that I have installed by default.
No matter how clean you want to leave a development environment, a package always slips into you ... thank you for your contributions.
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