systemtap-20060325 aborts if it does not find the kernel configured with "RELAY_FS". The message is "systemtap needs CONFIG_RELAYFS_FS in the kernel". As of 2.6.17 (and possibly before) that config option has moved and changed name. It is no longer in "Filesystems -> Pseudo filesystems -> Relayfs". It is now in "general setup" and it has the name "CONFIG_RELAY". I think Portage needs a more recent systemtap.
Created attachment 99850 [details, diff] systemtap-20061014.ebuild I didn't test it yet, but at least compiles and installs itself successfully on top of 2.6.18. Not sure if the >=virtual/linux-sources-2.6.18 check works but it didn't hurt.
thanks, fixed