The extconf.rb for OpenSSL assumes MingW
It appears that the extconf.rb file for openssl assumes mingw. The problem is that gdi32 and wsock32 need to be linked, even for Visual Studio.
The simple fix is to change "
if $mingw" to "
if File::ALT_SEPARATOR" on line 40.
Updated by djberg96 (Daniel Berger) about 4 years ago
Looking at the source code, File::ALT_SEPARATOR only appears to be defined on Windows. It's set in file.c if DOSISH is defined, and the DOSISH macro is set in defines.h if _WIN32 is defined.
In any case, it's definitely not limited to $mingw.