libxml2: meson options removed upstream, twice in a row

5. libxml2: meson options removed upstream, twice in a row

What happened, round 1:

meson.build:1:0: ERROR: Unknown option: "ftp".

What happened, round 2 (after fixing round 1):

meson.build:1:0: ERROR: Unknown option: "lzma".

Root cause: libxml2's meson options list isn't static across versions. FTP and LZMA compression support were both removed from libxml2's codebase around the 2.14/2.15 release series (confirmed by reading libxml2's own NEWS file and current meson_options.txt directly, rather than assuming from the error message alone) — not merely disabled by default, but deleted, so passing -Dftp=disabled or -Dlzma=disabled fails with "unknown option" since there's nothing left to configure.

What actually fixed this properly: rather than removing flags one at a time as each CI run surfaced the next missing one, we compared this project's libxml2.sh directly against mpv-android's own libxml2.sh — which only ever passed -Dminimum=true -D{push,reader,sax1,iso8859x,pattern}=enabled and nothing else. Simplifying to match that exactly (removing -Dhttp, -Dlzma, -Dzlib entirely, letting every optional feature default to whatever upstream's own "auto" resolves to) fixed it in one pass and is far more resistant to future libxml2 version bumps, since it depends on fewer options that could individually disappear.

Lesson: when a version-drift error appears, don't just delete the one flag the compiler complained about and move on — check whether a reference implementation (mpv-android, in this case) already solved the same problem more robustly, and whether other flags in the same command are equally fragile before the next CI run surfaces them one at a time.