romtool option 'kickety split' is broken

[erique]

Reproduction

romtool split -o /tmp/test-rom --no-version-dir "Kickstart v3.1 r40.070 (1994-02)(Commodore)(A4000T)[!].rom"
romtool build -k -o /tmp/rebuilt.rom /tmp/test-rom/index.txt
stat -f%z /tmp/rebuilt.rom
romtool info "Kickstart v3.1 r40.070 (1994-02)(Commodore)(A4000T)[!].rom"
romtool info /tmp/rebuilt.rom

Result

Rebuilt ROM size:

524292

(== 512 KiB + 4 extra bytes)

Original ROM:

size                  ok
header                ok
footer                ok
size_field            ok
chk_sum               ok
kickety_split         ok
magic_reset           ok
is_kick               ok

Rebuilt ROM:

size                  NOK
header                ok
footer                ok
size_field            NOK
chk_sum               ok
kickety_split         NOK
magic_reset           ok
is_kick               NOK