cygwin github action + sysoptions workaround

[brandonros]

I doubt this will get actually upstreamed but it helped me today so I hope it helps somebody else.

https://cygwin.com/packages/x86_64/cygwin-devel/cygwin-devel-3.4.9-1 says 2023-09-06 11:29 581 usr/include/sys/random.h is provided but autoreconf couldn't find it for some reason.

I also tried to do --enable-static (to avoid the need for the Cygwin runtime being installed/the binaries being linked externally against the Cygwin runtime DLLs) but it had a hard time with -lcrypto (it probably isn't provided in a fashion that can be used statically from https://cygwin.com/packages/x86_64/libcrypt-devel/libcrypt-devel-4.4.20-1 (although I do see usr/lib/libcrypt.dll.a)

How to use:

# build it with GitHub Actions + download: https://github.com/brandonros/dropbear/actions/runs/6964141533
# install Cygwin on the machine (probably need libcrypt package) or figure out Cygwin runtime DLLs
# run it from Cygwin terminal, not Git Bash or MinGW (freaks out about being able to write to /etc/dropbear for host keys)
mkpasswd -l > /etc/passwd
mkgroup -l > /etc/group
mkdir /etc/dropbear
mkdir ~/.ssh/
vi ~/.ssh/authorized_keys # paste ~/.ssh/id_rsa.pub from client into it, do not try to connect with passwords
./dropbear -F -E -R -w -s -g -j -k

[mkj]

If you still have config.log handy, can you send it? It might show why sys/random.h isn't being found.