Actually store result for add

[Grazfather]

No description provided.

[ikskuh]

Can you add a test which validates that the error won't happen again?

[Grazfather]

Done

✦ ❯ zig build test
test
└─ run aviron-test-runner failure
stderr mismatch:
expected: 'Hi'
actual:   ''4'
test instructions/add.S failed.
error: the following command exited with code 1 (expected exited with code 0):
/Users/graziano/code/CTFs/rhme3/2025/aviron/.zig-cache/o/d454b9502e0bd8fff094e5db46f4b2b1/aviron-test-runner --config /Users/graziano/code/CTFs/rhme3/2025/aviron/.zig-cache/o/d4cc0eda316a771a6547acfce708da3e/config.json --name instructions/add.S /Users/graziano/code/CTFs/rhme3/2025/aviron/.zig-cache/o/f1939522e8b5d085e1b1bcbf3cbb931e/add
Build Summary: 85/87 steps succeeded; 1 failed
test transitive failure
└─ run aviron-test-runner failure
error: the following build command failed with exit code 1:
/Users/graziano/code/CTFs/rhme3/2025/aviron/.zig-cache/o/31cc2853b1d368b91ccd23a0688abfb1/build /Users/graziano/.local/share/zigup/0.14.0/files/zig /Users/graziano/.local/share/zigup/0.14.0/files/lib /Users/graziano/code/CTFs/rhme3/2025/aviron /Users/graziano/code/CTFs/rhme3/2025/aviron/.zig-cache /Users/graziano/.cache/zig --seed 0xa6cae8ed -Zb41c868321fafad1 test

✦ ❯ git co -
Previous HEAD position was 579db2f Add test for add/adc

✦ ❯ zig build test