switch to https default + use argument lists to support spaces in the path

@mortenvp I managed to compile sak with a space in the path ;)
Basically, the Utils.to_list(cmd) function should be avoided at all costs, because it splits the command at the spaces.
Whenever we interact with waf, we have to pass the arguments in a list, not as a single string.

I also had to change one thing in the wscript recurse_helper (this should be done for all projects):
ctx.recurse(p) => ctx.recurse([p])

Fortunately, the compiler invocation was just fine with the spacey paths.
Well, the msvc compiler itself is in "Program Files", so it works without issues ;)