[libxml2] cmake: Install documentation in CMAKE_INSTALL_DOCDIR

[Nick Wellnhofer <nwellnhof src gnome org>]

commit a5724a3b4aba00a7ceebe8cefe3f589568cf50f2
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Fri Apr 8 15:46:26 2022 +0200

    cmake: Install documentation in CMAKE_INSTALL_DOCDIR
    
    Sync with recent Autotools change.

 CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 086952b4..4cd2db91 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -600,7 +600,7 @@ endif()
 install(FILES doc/xml2-config.1 DESTINATION ${CMAKE_INSTALL_MANDIR}/man1 COMPONENT documentation)
 install(FILES doc/xmlcatalog.1 DESTINATION ${CMAKE_INSTALL_MANDIR}/man1 COMPONENT documentation)
 install(FILES doc/xmllint.1 DESTINATION ${CMAKE_INSTALL_MANDIR}/man1 COMPONENT documentation)
-install(DIRECTORY doc/ DESTINATION ${CMAKE_INSTALL_DATADIR}/doc/libxml2 COMPONENT documentation
+install(DIRECTORY doc/ DESTINATION ${CMAKE_INSTALL_DOCDIR} COMPONENT documentation
        PATTERN "Makefile.*" EXCLUDE
        PATTERN "*.1" EXCLUDE
        PATTERN "*.py" EXCLUDE