Thanks for the link, but I really just wanted to do it myself as a learning opportunity. It didn't occur to me that since I've already compiled the binaries (several times now,) I should have that file myself, right? I'll have a look when I get home.
Not necessarily... unless you have explicitly installed the appropriate libraries, the Windows build will still complete "OK" (with errors that scroll past) and binaries will be built... but the libsecp256k1 stuff will be missing and you'll get errors when you try to run it... as per this post:
https://bitcointalk.org/index.php?topic=5222986.msg53807327#msg53807327If you have "libsecp256k1-dev" installed in Ubuntu (with apt-get)... and the python library "libsecp256k1" installed (with pip)... then the build-wine process will automatically compile the libsecp256k1-0.dll and roll it into your binary file. You can also find this compiled .dll and then copy it to a Windows machine and put it into your Electrum "source" folder to be able to run from source.