fix: strip .sframe from glibc crt objects to unblock Zig linker on GCC 15+

[codemedic]

Stacks on top of #140.

Problem

GCC 15+ compiles glibc crt startup objects (crt1.o, Scrt1.o, rcrt1.o) with .sframe sections that use R_X86_64_PC64 relocations. Zig's self-hosted linker doesn't support this relocation type, causing build-time helpers such as ghostty-build-data to fail:

error: fatal linker error: unhandled relocation type R_X86_64_PC64 at offset 0x1c
    note: in /usr/lib/gcc/x86_64-pc-linux-gnu/15.2.1/../../../../lib/crt1.o:.sframe

The same root cause has been discussed at https://ziggit.dev/t/linker-error-when-building-zig-from-source/14394 and a matching fix has been approved upstream in ghostty itself (ghostty-org/ghostty#11993) — but that only helps tip builds once it lands; stable releases need a workaround at the build-script level.

Fix

In setup-env.sh, immediately after pacman installs packages, use objcopy (already available via binutils/base-devel) to strip .sframe and its associated relocation section .rela.sframe from the three affected crt objects:

for _crt in /usr/lib/crt1.o /usr/lib/Scrt1.o /usr/lib/rcrt1.o; do
    [ -f "$_crt" ] && objcopy --remove-section .sframe --remove-section .rela.sframe "$_crt"
done

This is version-agnostic — it works for GCC 15, 16, and beyond without requiring any changes to the Zig invocation or ghostty's build system.

Also removes URUNTIME_PRELOAD=1 from bundle-appimage.sh. The aarch64 dwarfs-lite uruntime variant (v0.5.7) does not support the URUNTIME_MOUNT marker patching that flag triggers, causing AppImage packaging to fail on aarch64.

Tested

Full green CI run on both x86_64 and aarch64 (stable build, v1.3.1):
https://github.com/codemedic/ghostty-appimage/actions/runs/25518466177