step1、install Xcode

step2、install xcpkg

step3、update xcpkg-formula-repository

xcpkg update

step4、build and install expat

xcpkg install expat

xcpkg formula view expat

{{ formula }}

if the formula of expat dosn't meet your needs, you can edit it ⤵︎

xcpkg formula edit expat

after editing, you may want to rebuild this package ⤵︎

xcpkg install expat