I work in the gaming (Gambling) industry.
Many states require us to submit both the source code and build tools required to make an exact (and I mean 'same md5sum') copy of the binary that is running on a slot machine on the floor.. to an extent that would blow you away.
They need to be able to go to the floor of a casino, rip out the drive or card containing the software, take it back to THEIR office, and build another exact image of the same drive or SD card.
md5sum from /dev/sda and /dev/sdb must match.
I can tell you the amount of effort that goes into this is monumental. There can be no dynamically generated symbols at compile time. The files must be built compiled and written to disk exactly the same every time. The filesystem can't have modify or creation times because those would change.
This is a silly idea for open source software, the only industry I've seen apply it is perhaps the least-open one in the world.