Fix Azure pipeline introduced by only checking out a single repository.

If checking out a single repository, the repository is checked out
to the path $(Agent.BuildDirectory)\s instead of
$(Agent.BuildDirectory)\s\<name of repository>.  Modified checkout
to hard code path to avoid this change in behavior.

azure-pipelines.yml

@@ -21,6 +21,7 @@ resources:
 steps:
 - checkout: git://NetHack/NetHack@NetHack-3.7  # $(Agent.BuildDirectory)\s\NetHack
   submodules: true
+  path: NetHack
 
 - task: DownloadSecureFile@1
   name: storeKey