Add configurable T2C optimization level

[jserv]

This introduces CONFIG_T2C_OPT_LEVEL (0-3) to control LLVM optimization passes in T2C compilation. O1 provides ~50% faster compile time compared to -O3 while maintaining correctness.

It reduces CI time for T2C boot tests without sacrificing runtime performance in production builds (jit_defconfig still uses -O3).

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Summary by cubic

Add a configurable LLVM optimization level for T2C (CONFIG_T2C_OPT_LEVEL 0–3) and use O1 in system_jit_defconfig to speed up CI boot tests without impacting production performance. O1 cuts T2C compile time by ~50% vs O3.

• New Features
  • Kconfig adds T2C_OPT_LEVEL (0–3, default 3); Makefile passes it as CONFIG_T2C_OPT_LEVEL.
  • t2c.c selects the LLVM pass pipeline based on the level and validates the range; defaults to O3.
  • system_jit_defconfig sets level 1; CI BOOT_TIMEOUT reduced from 150 to 120.

^{Written for commit 20f4411. Summary will update on new commits.}

[cubic-dev-ai]

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