I just had a quick look into the screenshot you provided and It appears that build script is looking for an "src" folder to compile the soure files. From the screenshot src looks like a softlink you have setup to point to the location of your source folder. You can do the following:
1. Right click on the project in your eclipse and go to Properties --> Java Build Path --> Source tab and identity the location where the src link is pointing to (actual physical folder where the source files are present)
2. Update your build.xml with this location.
so, if you have <property name="src" value="src"/> change this to <property name="src" value="PHYSICAL LOCATION OF SOURCE FILES"/>