The trend of packaging is to hide more and more of what actually happens
behind helper macros and other dynamically generated constructs. While
this is mostly a good thing, it makes understanding and postmortem
analysis harder than it should be. Add the spec in its parsed and
expanded form into the src.rpm header to make the actual contents of the
build more trackable.
It can be argued this does not belong in the header and should be in
payload instead, my rationale for the placement is that this way the
payload remains effectively arch independent, whereas the header already
heavily reflects the particular environment where it was built.
Probably worth noting that %setup and %patch built-in macros are not
properly expanded in the stored spec, but that's a separate issue
related the special way %prep is processed.
Fixes: #1241
122bb4ffae