[nickyyOO]

Before

Every open-source toolchain file came from one upstream link. If that link went away (the EE GCC source already lives only on archive.org), setup stopped.

After

lombyte-project/toolchain-mirror keeps a copy of each open-source file with its license and source, and explains the toolchain choices. When an upstream download fails, the setup tries the mirror, pinned to a commit:

• setup.sh: binutils, objdiff, and the GCC 2.95.2 headers (when the SDK mirror clone or checkout fails). When both fail, setup stops with "could not download" instead of a hash error.
• scripts/build-game-compiler.py: the EE GCC 991111b source, bison 1.28
• scripts/build-sn-compiler.py: gcc-2.95.2
• docs/build/building.md: one line about the mirror

The SHA-256 pins are the same. Sony's and SN's binaries are not in the mirror; setup still fetches them from their public sources.

Verification

• Each fallback tested with a dead upstream URL: the file came from the mirror and passed its pin. A dead URL with no mirror copy stops with a clear error; the normal SDK header checkout still works.
• scripts/test_public_tools.py passes in CI (tools).
• No build output changes (download code only); make elf not rerun.

[github-actions]

Decompilation progress

	C_EXACT	Change	Matched bytes	Functions	C_FUZZY
All code	100.00 %	—	3,547,932 / 3,547,932 B (—)	4,244 / 4,244 (—)	100.00 %
Boot executable	100.00 %	—	354,504 / 354,504 B (—)	1,230 / 1,230 (—)	100.00 %
Game	100.00 %	—	264,872 / 264,872 B (—)	850 / 850 (—)	100.00 %
SDK	100.00 %	—	89,632 / 89,632 B (—)	380 / 380 (—)	100.00 %
Level overlays	100.00 %	—	3,193,428 / 3,193,428 B (—)	3,014 / 3,014 (—)	100.00 %
Shared level code	100.00 %	—	1,130,492 / 1,130,492 B (—)	1,583 / 1,583 (—)	100.00 %
Per-level code	100.00 %	—	2,062,936 / 2,062,936 B (—)	1,431 / 1,431 (—)	100.00 %

	Data in C	Change	Matched bytes
All data	62.81 %	—	7,809,078 / 12,433,372 B (—)
Boot executable	26.98 %	—	188,645 / 699,136 B (—)
Level overlays	64.94 %	—	7,620,433 / 11,734,236 B (—)

No function changed its match state compared with main (a23dc98).

_{Compared with main (a23dc98). C_FUZZY uses main's last measurement.}