- we've had SKIP_EXTERNAL_TOOLCHAINS=yes for ~5 years now
- drop all usages, mostly through `find_toolchains()`
- drop all manual PATH env injections (we've centralized if ever needed)
Update all copyright notices in shell scripts from 2025 to 2026.
## Changes
- **Igor Pecovnik**: 2013-2025 → 2013-2026 (129 files)
- **Ricardo Pardini**: 2023-2025 → 2023-2026, 2020-2025 → 2020-2026 (5 files)
## Additional Improvements
Also updated the backtitle in `lib/functions/configuration/interactive.sh`:
- Changed title from "Armbian building script" to "Armbian Linux build framework"
- Removed docs link for cleaner display
- Uses dynamic year calculation with separate declaration (fixes shellcheck SC2155)
