redland/raptor: use system xml2-config only on MacOSX

On Fedora 30, we get:

instdir/program/libraptor2-lo.so.0 has suspicious NEEDED: liblzma.so.5

Because:
> xml2-config --libs
-lxml2 -lz -llzma -lm -ldl

However:
> pkg-config --libs libxml-2.0
-lxml2

So prefer pkg-config for system libxml2, except on MacOSX, where
people claim that pkg-config leads to disaster.

Change-Id: I29ffd2ced769d7111c4de17de53082db2e2ba326
Reviewed-on: https://gerrit.libreoffice.org/77093
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
(cherry picked from commit 1067c32964e4e0754d2d926e1319b4060ded93f5)
Reviewed-on: https://gerrit.libreoffice.org/77099
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

0 files changed, 0 insertions, 0 deletions