To those who need to install libtidy on mac os x , here is a guide that worked for me :
If you're on Mac OS X, you'll need to tell the Makefile that you use
ranlib:
$ export set RANLIB=ranlib
Change to the directory with the Makefile in it, and run make.
This example uses the GNU make Makefile.
$ cd tidy/build/gmake/
$ make
if [ ! -d ./obj ]; then mkdir ./obj; fi
gcc -o obj/access.o ...
... etc etc etc ...
Install the libs, headers and the tidy executable:
$ sudo make install
If you're on Mac OS X, you'll have to run ranlib again on the installed
lib:
$ sudo ranlib /usr/local/lib/libtidy.a