Add Troubleshooting a failed build
The fourth page GH-96 named, deferred then because its material was scattered
across BUILDING.md, the log/stamp mechanics, and failure modes written down
nowhere at all.
Every message it quotes was read out of the source or reproduced, not recalled:
- the log lifecycle, from run() in lib/utils.sh -- a surviving log IS the
failure, because a successful recipe deletes its own
- "outdated but will not be rebuilt" (lib/utils.sh:229), the skip that
continues the build with the old library and fails nothing
- "refusing to produce a mixed-level workspace" (mediaforge.sh:473-481)
- the missing-.dwo symptom, reproduced by hiding one .dwo and re-running gdb:
the warning is followed by "No breakpoints, watchpoints, tracepoints, or
catchpoints" -- the breakpoint is silently not set
Also names the licence-tier trap: save_stored_choices persists the six group
choices and the trust-store path, and NOT --enable-gpl/--enable-nonfree, so a
bare rebuild after a nonfree build resolves a different recipe set. Verified by
reading the heredoc rather than assumed.
Links to BUILDING.md for per-distribution static-build setup rather than
restating it, per the GH-96 carve-out.
Refs #99
Claude-Session: https://claude.ai/code/session_019T1bLfDhuHJpNNhn8CHVLJ