Generate x86 build of host EXE using corflags.exe

[daviwil]

Instead of having a duplicate .csproj to build the x86-only EXE, it's more convenient to use corflags.exe to generate the x86 version from the AnyCPU version. I do this in the PowerShell ISE Preview build and it seems to be working really well so far.

One other benefit of this change is that both of the EXEs will end up in the same PowerShellEditorServices.Host\bin* folder which makes it easier to set a path to the x64/x86 binaries in VS Code when testing different architectures.