Add BIOS and tiny kernel roadmap phases

Tutorial/phase-08-gcc-toolchain/phase-08-02-first-gcc-program.md

@@ -27,7 +27,7 @@ every emitted instruction is implemented or fails loudly.
 
 - Compare C source to generated assembly.
 - Identify every load/store used for UART access.
-- Confirm no CSR or `fence.i` instructions appear before Phase 9.
+- Confirm no CSR or `fence.i` instructions appear before Phase 12.
 
 ## Pitfalls