httpd: use correct libxml2 (#9684)
httpd: use correct libxml2 (#9684)

httpd.rb was always using the system's libxml2 during ./configure instead of the version installed by homebrew.
Fixes https://github.com/Linuxbrew/homebrew-core/issues/9205


maxim-belkin/homebrew-core,maxim-belkin/homebrew-core,LinuxbrewTestBot/homebrew-core,LinuxbrewTestBot/homebrew-core,rwhogg/homebrew-core,Linuxbrew/homebrew-core,Linuxbrew/homebrew-core,rwhogg/homebrew-core