when a declaration created on the fly (not loaded from FIR), we
have no good way (yet) to create a correct signature for it before
creating IR. And proper signatures are needed for Klib linking.
So here we create the declaration (function) twice, first time
to calculate proper signature and the second time again with correct
signature.
The approach is weird and should be unnecessary in the presence of the
stdlib, so should be doublechecked again in the future.
Ilya Chernikov
af5d74e888