I had the same problem, I was using 17.12.03 version and It gave:
Buildfle: build.xml does not exist!
Build failed
So I switched to 16.11.01, and lucky I was blessed with same obstruction again.
So I got my hands dirty and Finally Installed it by following steps:
Make the Apache_Ofbiz folder as CURRENT DIRECTORY.
"./gradle/init-gradle-wrapper.sh" (it may take some time depending upon internet connection)
Make sure you have java version < 14 (as Gradle still does not support java 14) if not downgrade it with following steps:
sudo apt-get update
sudo apt-get install openjdk-8-jdk
sudo update-alternatives --config javac
select jdk8
sudo update-alternatives --config java
select jre8
now java -version to confirm changes
"./gradlew ofbiz" (it may take some time depending upon internet connection)
Done
Just visit https://localhost:8443/ordermgr or go through README
Now I got the latest version install by following above steps.