This commit allows any electron user to compile electron
artifacts by themselves in production mode. When the source code
is reproducibly buildable with a given toolchain this change
allows them to verify the hash of their build, with the same
windows toolchain agains the CI version.
This change was tested on top of version fb9837799b
which was buildable and reproducible for chromium and electron as well.
Further tests may be introduced to allows checking for local reproducibility.
EG: building twice an artifact on the same machine, with different time
and output directory should yield similar hashes.
