To install LibSass, make sure the OS X build tools are installed:

xcode-select --install

Homebrew

To install homebrew, see http://brew.sh

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

You can install the latest version of LibSass quite easily with brew.

brew install --HEAD libsass

To update this, do:

brew reinstall --HEAD libsass

Brew will build static and shared libraries, and a libsass.pc file in /usr/local/lib/pkgconfig.

To use libsass.pc, make sure this path is in your PKG_CONFIG_PATH

export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig

Manually

See the linux instructions Building-with-autotools or Building-with-makefiles