> -d:ssl
This is same with `--define:ssl` , two hyphens is long option while single
hyphen is short option.
This `--define` option is to define a compile-time variable ala `#DEFINE` in C
for example you define 'goThisWay' when compiling then you can use it in code
when defined(goThisWay):
# all codes that will be compiled
else:
# alternative when you want other codes
Run
Another use is explained in this [part of
manual](https://nim-lang.github.io/Nim/manual.html#implementation-specific-pragmas-compile-time-define-pragmas)
