…o xtrans

I *think* the way I've done it, conda will not become convinced that the
package needs to be built for multiple Python versions? Let's find out.

You know, I noticed that I overlooked the '|lower' but I thought to myself
that there was NO way that would ever come back to bite me. Well, here we are.

Looks like I need toolchain packages, and I need to build for all of
the Visual Studio variants.

Windows builds delegate to the build.sh script, but that meant that build.sh was
getting environment variables like $PREFIX with Windows-style paths. Problems
if they were ever echoed, etc. Transform the key paths in bld.bat, then. We also
add the -x option when running bash on the build script so we can trace it better.

Since where are things that basically do `echo $(which programname)` in
configure scripts. I wonder whether our setting of %PATH% in the batch script
will mess it up? Let's find out.

Also I highly suspect that you have to add Python as a build-time dep to get
the builders to matrix across the different 'vc' versions.

Not optimistic this will fix my current build error, but if the Cairo
experience is right, this change is important anyway.

xtrans.m4 checks for being on Windows by looking for mingw, not msys, so its defaulting
doesn't work.

So it turns out that on Windows alone, libICE depends on libX11 to build. So I
need to do a different direction down the stack to get those things going. So
let's just get the next three packages in for now.