RENPY_DEPS_INSTALL uses "::" to separate paths instead of os.pathsep

[Uzume]

I considered directly making a pull request but I instead decided to first bring the issue up here for discussion in case there is some amazing good reason for this that I cannot understand.

It seems os.pathsep is designed exactly for this purpose so this seem like a bug to me.

For reference RENPY_DEPS_INSTALL seems to have been introduced in 2006 f9bb838 but :: path separation syntax was first introduced in 2009 a0fda2f

[renpytom]

Not a good reason, other than perhaps os.pathsep not existing (or more likely, me not knowing about it) when that was written. I made the change, as I wanted to make sure we still support :: for compatibility with scripts that build Ren'Py.

[Uzume]

I had a feeling there were probably some external build script dependencies and exactly why I brought it here instead of directly making a pull request.

Thanks for the quick turn around.