Interesting point Siekla19 , the most likely path to do a build for HoloLens 1 would require you to use the original "HoloToolkit" (precursor to the Mixed Reality Toolkit)
Release HoloToolkit 2017.4.3.0 - Refresh ยท microsoft/MixedRealityToolkit-Unity (github.com)
(above is the final release for the HoloToolkit)
You will also need to use the latest Unity 2017 LTS build (newer versions "might" still work, but not sure).
As well as Visual Studio 2017 and the Windows SDK 10.0.17134
It has been a while since I tried deploying to my HL 1, but the above should work best. Early versions of the MRTK2 did still support HoloLens 1, but I'm not sure about its state in the finished MRTK2 releases.
Good luck and let us know how you get on and feel free to reach out on the HoloDevelopers slack channel for further questions.