textproc/libxml2: fix build with lld 17

Many symbols in the linker version script libxml2.syms are only defined
when --with-xptr-locs is enabled at configure time. Since version
scripts do not support conditionals, suppress errors with lld >= 17 due
to these undefined symbols.

PR: 273789
MFH: 2023Q3
Approved by: blanket (for desktop and kde)