This is a new version of the build script that was born out of the old Kdenlive Build Wizard and published as a standalone Bash script elsewhere here on the forum. I am not maintaining the script and making the latest version available for download from the MLT wiki:
http://www.mltframework.org/twiki/bin/view/MLT/BuildScripts#Kdenlive

Your script is outdated due to the ffmpeg git repo location changing. Please download a new version. Also, 'rm -rf src/ffmpeg' from the location where you are placing and running the script.