Following your post I tried it but without joy. I then created a new FreeBSD 9.2 machine from scratch and run "portsnap fetch extract" before installing the build tools. Nonetheless I encountered exactly the same error. Then I build FreeNAS by issuing the "make NO_CHECKSUM=yes release" command to circumvent the checksum error but then got the following error:Did you try reinstalling ports? > portsnap fetch extract
extracting for ataidle-2.7.2 unrecognised archive format
I'm starting to wonder whether FreeBSD introduced a problem with "ataidle" between now and then and this problem is not really related to the Xen settings.
Below is the link to my GitHub repository where you can see what changes I applied https://github.com/topler/freenas-9.2-xen/compare
I presume my problem is related to my build environment rather to the Xen Server related changes since a normal build without those Xen Server related changes gives the same error.
If someone fancy, you could also run the build by using this repository on https://github.com/topler/freenas-9.2-xen. If you build environment doesn't have this glitch I have, I believe it should go through just fine.
git clone -b xenserver https://github.com/topler/freenas-9.2-xen.git