I have done all kinds of research and tried many different things. I know this question has been answered many times, but none of the suggested solutions are working for me.
OS: Catalina
Warning: warning nokogiri was built against libxml version 2.9.10 but has dynamically loaded 2.9.4
I followed Michiel de Mare steps, but brew install libxml2 --with-xml2-config failed with invalid option error. So I installed libxml2 and libxslt and took note of the output from both commands.
brew install libxml2
==> Downloading https://homebrew.bintray.com/bottles/libxml2-2.9.10_2.catalina.bottle.tar.gz
Already downloaded: /Users/alberto/Library/Caches/Homebrew/downloads/9ddf5cb90fd16a7eb531e37bb748fd392f30214d9fe1568b2b70d28cc368c8f7--libxml2-2.9.10_2.catalina.bottle.tar.gz
==> Pouring libxml2-2.9.10_2.catalina.bottle.tar.gz
==> Caveats
libxml2 is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
If you need to have libxml2 first in your PATH run:
echo 'export PATH="/usr/local/opt/libxml2/bin:$PATH"' >> ~/.zshrc
For compilers to find libxml2 you may need to set:
export LDFLAGS="-L/usr/local/opt/libxml2/lib"
export CPPFLAGS="-I/usr/local/opt/libxml2/include"
For pkg-config to find libxml2 you may need to set:
export PKG_CONFIG_PATH="/usr/local/opt/libxml2/lib/pkgconfig"
==> Summary