vienna2025: Add D3 definition workgroup notes

# Definition of Reproducible Builds (day 3 morning session)

A build is reproducible if given the same:

- source code

- build environment

- build instructions

any party can generate bit-by-bit identical copies of all specified artifacts.

main page

RB are a set of software dev practices that create an independently verifiable path from source to binary code.

- a mathemathicaly definition that

- RB process should be repro

- human verifiable inputs, process, and bit-by-bit identical output

- "Why?" should be in definition

- source code doesn't abstract world cases (binary)

- the definition doesn't hold for everyone