[DEVOPS-223] AppVeyor: stack 1.5.0 upgrade (#405)
[DEVOPS-223] AppVeyor: stack 1.5.0 upgrade (#405)

* [DEVOPS-223] AppVeyor: stack 1.5.0 upgrade

In stack v1.4.0 the stack executable was in the root of the downloaded
zip, but now in stack v1.5.0 it's under the stack.exe directory. The
link we're using now resolves to stack v1.5.0.

* [DEVOPS-223] AppVeyor: stack 1.5.0 install logic

input-output-hk/daedalus,input-output-hk/daedalus,input-output-hk/daedalus,input-output-hk/daedalus,input-output-hk/daedalus,input-output-hk/daedalus