Add cross compiling support for MSVC.

[xpol]

This is needed, when native compiler is not installed but cross compiler does.

See #534.

[mpeterv]

Thank you @xpol! Haven't tested this yet but it looks good. By the way, is there a reason why install.bat is both a batch file and a Lua script? It messes up syntax highlighting a lot. Would it make more sense to move the Lua code into install.lua and call that from install.bat?

[mpeterv]

Tested, it works.

[xpol]

I just choose syntax manually.
I think it is good to separate bat and Lua. But I don't known how it works, I just update it.

[xpol]

i tested with vs2013.

[Tieske]

By the way, is there a reason why install.bat is both a batch file and a Lua script?

The installer used to be a batch file, but it was very cumbersome and hard to maintain, so it was rewritten as a Lua file (by @ignacio). I for one would like to keep it this way, the repo is already dragging so much files along, keeping this in one file is a bigger benefit than the syntax highlighting imo.

[mpeterv]

@xpol I think we also need to ensure that these scripts that we now use directly exist for all VS versions, because unlike vcvarsall.bat their paths are not documented. Or, better, fall back to vcvarsall.bat if arch-specific scripts are not found.

[hishamhm]

I want to make a new minor release. Windowsfolk, is this good for merging?

[xpol]

@mpeterv
commit 11b65a6 has fallback to documented vcvarsall.bat when the undocumented bats not found.

[mpeterv]

Tested this locally with some VS versions and on appveyor with all combinations of VS version/arch.