Suppress .eh_frame generation when EXECUTORCH_OPTIMIZE_SIZE is ON

[lucylq]

Add -fno-asynchronous-unwind-tables and -fno-unwind-tables to both
CXX and C release flags when EXECUTORCH_OPTIMIZE_SIZE is enabled.
This eliminates .eh_frame/.eh_frame_hdr sections from the runtime
libraries, which is safe because ExecuTorch already builds with
-fno-exceptions.

For each function, .eh_frame stores a compact description of how to restore the previous stack frame

• where registers are saved
• how to find the return address
• how the stack ptr changed for each instruction.

Caveats, when OPTIMIZE_SIZE is on

• Can't run gdb
• Can't run perf tooling

Reduces stripped size_test by 8,192 bytes (14.6%) and stripped
size_test_all_ops by 143,360 bytes (8.6%).

[lucylq]

Stack from ghstack (oldest at bottom):

• Mark Kernel and KernelKey constructors constexpr #17909
• Use direct function pointers for et_copy_index and et_view in prim_ops #17908
• Export ET_LOG_ENABLED=0 as PUBLIC compile definition on cmake targets #17907
• -> Suppress .eh_frame generation when EXECUTORCH_OPTIMIZE_SIZE is ON #17906

[pytorch-bot]

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⚠️ 1 Awaiting Approval, 36 Pending

As of commit f613426 with merge base 411061f ():

AWAITING APPROVAL - The following workflow needs approval before CI can run:

• Claude Code (gh)

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[Copilot]

PR description says the change only adds -fno-asynchronous-unwind-tables/-fno-unwind-tables, but this hunk also adds -fno-exceptions and -fno-rtti to CMAKE_CXX_FLAGS_RELEASE. Please update the PR description (or drop the extra flags) so reviewers/users understand the full behavior change.