I finally found the courage(!) to dig the commit out of my reflog that had my previous attempt to statically link GNU libiconv into recode.
I confess that I don't understand what is going on here: recode's configure seems to be trying to configure libiconv/libcharset. I don't know why it does that on Windows, nor why it doesn't on GNU/Linux and macOS.
I'll be very grateful for any help you can give! I hope the approach (to statically link libiconv, installed with "make install-lib" is at least correct now.
I look forward to getting past this build system pain and into implementing some improvements to Recode, such as the one you proposed recently. With a known iconv "under the hood" I look forward to being able to remove Recode's own support for character sets that are perfectly well supported by GNU libiconv, and concentrating on what Recode can do that libiconv can't.