NOTE: For the free version of the Leda library, you don't have to build the package to use the library. It simply doesn't work.
To use the library simply include it in your compile line and linker.
If you are compiling from the shell (assuming you are using Linux), do the following:
1. Set the env variable to the library folder e.g export LEDAROOT= /path/to/Leda
2. Set the LD_LIBRARY_PATH env variable e.g export LD_LIBRARY_PATH=$LEDAROOT
Verify that this variables are set then you can compile and link and run. You can simply do
CC (g++) -I$LEDAROOT/incl -L$LEDAROOT file.c -lleda -lX11 -lm
With this you should be good to go.
If you are using an IDE, simply add the include path (i.e /path/to/leda) to you project settings.
This is all you have to do. Building the library does not work. Simply include it