I see that 26 modules use it in Makefile.
On the other hand, on macos, the output of xml2-config and pkg-config are different:
``` $ xml2-config --libs -L/opt/local/lib -lxml2 -L/opt/local/lib -lz -L/opt/local/lib -llzma -lpthread -liconv -L/opt/local/lib -licui18n -licuuc -licudata -lm
$ which xml2-config /opt/local/bin/xml2-config
$ pkg-config --libs libxml-2.0 -L/opt/local/lib -lxml2
$ which pkg-config /opt/local/bin/pkg-config ```
On debian 10 is the same.