[wix-devs] Building from the VS developer command prompt

[Bob Arnson]

One of the problems we've run into with VS2017 is that not only are directories not centralized, many are now versioned and those versions have changed in the two updates that VS2017 has shipped so far. So I decided to look at building from a VS developer command prompt, letting it "find" the right paths for us, instead of the current approach of having the WiX build tools do the hunting. The downside is that if we do this, you won't be able to build WiX from any ol' command prompt. The upside is that I won't have to maintain a supported list of Windows SDKs forever.

I have a work-in-progress branch for building with the VS command prompt at https://github.com/barnson/wix4/tree/vs_dev_command_prompt. More work to do but that branch currently builds all of WiX on VS2017. But right now, I don't have a machine with multiple versions of VS installed, so:

1. I don't know if this broke multitargeting for *Util native libraries.
2. I don't know if this approach works with other versions of the VS command prompt.

Anybody with spare time and a machine with multiple VSes who could try out a build from my branch and report back? I have virtual cookies to share!