Add dead-strip / split-sections for iOS builds

[jappeace-sloth]

Problem

PR #196 adds -split-sections + --gc-sections for Android .so builds, reducing binary size by ~40-60%. The iOS builds don't have equivalent size reduction.

Context

• On iOS/macOS (Mach-O), the equivalent of --gc-sections is -dead_strip on the Apple linker (ld64)
• GHC's -split-sections may be buggy on macOS/Darwin targets — a GHC maintainer has indicated this
• -dead_strip on the linker side should be safe independently of -split-sections

Possible approach

1. Add -dead_strip to the iOS linker invocation (safe, works at per-object granularity)
2. Optionally test -split-sections on Darwin — may produce linker errors or miscompilations
3. Could gate -split-sections behind a platform check (Linux/Android only) until GHC stabilizes macOS support

References

• Add -split-sections + --gc-sections for Android .so builds #196 (Android split-sections PR)