Scan the consolidated .data buffer (post-relocation) for trailing zero
bytes; set the R+W PT_LOAD's p_filesz to exclude them while p_memsz
covers the full region. The loader zero-fills the gap, so behaviour is
unchanged. Saves up to a page per binary on programs whose globals are
zero-init.
Mirrored in selfhost/cmd/w6l/out.ww so test 992's byte-identity diff
still holds. Dynamic-link path is untouched — it still errors on any
mutable global; that's the next feature.
Hojun-Cho
2480f4c272