Fix not passing -arch

[roblabla]

Looks like when I did the last rebase in #113 (over the reformatting commit), I forgot to re-add the -arch argument. Oops. This caused the Wix to always build 32-bit MSIs. This fixes it.

[volks73]

We may need to review all of the tests and see how this slipped through. I would think one of the integration tests would have been able to pick up that 32-bit MSIs were being created instead of 64-bit MSI when requested, but this would be for a different issue/PR.

I was going to merge, but there are some failing tests.

[roblabla]

So, the problem boils down to the generated MSI not being actually tested/installed. I think it might be a good idea to add a test that actually runs the MSI through msiexec, and checks that it gets installed properly, and at the right locations. So for a 64-bit executable, it should check that it gets installed in C:\Program Files, while on 32-bit it goes in C:\Program Files (x86).

What's nasty about this bug is that it actually generates a somewhat working MSI. It would just install the wrong things in the wrong places!

I think I fixed the failing test (wix doesn't understand -arch=x64 argument, have to split it in two).

[volks73]

Thanks for fixing the tests.

I think we could move the creation of the "build" Command type to a method within the Execution struct that returns the cmd ready to execute. Then, a unit test could be added to make sure the flags, options, values, etc. that are passed to candle and light is correct. This would at least prevent the -arch being dropped.

I do think at least one test that runs an install is needed, just as a sanity check. I will create an issue to discuss/track.