I am having this same issue right now and just cannot find a way to fix it other than hacking the build files.
I am using CentOS 6.3, PHP5.3 and trying to do some testing for a UPS Quantum View project.
It seems to me like this issue has never really been resolved as I find references to it all over.
I guess the only solution I have found to far is to not use the extension at all and instead use a more generic XML builder.
If I come across anything useful I will update here.
[EDIT] OK, I just came across this: https://groups.google.com/forum/#!topic/phpsoa/HQVxiBmsFv0