On line 32 of HoudiniEngine/Source/HoudiniEngine/HoudiniEngine.Build.cs change
string HFSPath = “C

to
String HFSPath = “”;
(this causes the auto-detection to kick in properly, or at least appears to)
damian
Thanks for bringing this up. We'll fix it for the next nightly.
In general though, our recommendation is that if you want to compile the plugin from source that you do it using the source code from our Github page:
https://github.com/sideeffects/HoudiniEngineForUnreal [github.com]
It should not have this problem and if you ever want to contribute anything it makes that process easier.
Update: This has been fixed as of 14.0.296.