Most of Eclipse plugins are marked as noarch, while the pdebuild script is actually arch specific. It is possible that wrong version of pdebuild script is installed on a build server, or the package refers to the wrong version (f.e. 32 bit build refers to the 64 bit path), and the build fails.
I don't see how can this happen. We evaluate the path to pdebuild to always be _libdir/eclipse/buildscripts/pdebuild.sh so the only possibility for this to happen is _libdir giving wrong value aka /usr/lib on 64bit or /usr/lib64 on 32bit which is something that I haven't seen in quite some time.
I have seen this with mylyn quite often. I have found multiple reports that when a noarch package is being built, its dependencies can be satisfied either by x86 or by x86_64 package, and they are not matches with the builder platform. I think we need to use ISA macros: http://rpm.org/wiki/PackagerDocs/ArchDependencies
The problem is solved by: * installing the pdebuild script into bindir (bug 790733) * having special eclipse macro that is correctly resolved when building noarch packages.