[libvirt] make dist failed

[Wen Congyang]

Another building error:

error: parse error in expression
error: /data1/wency/libvirt/libvirt.spec:138: parseExpressionBoolean returns -1

But I cannot reproduce this problem on another machine.

Steps to reproduce it:
1. ./autogen.sh
2. make dist
3. rpmbuild --define "_sourcedir `pwd`" --define "_without-numad 1" -ba libvirt.spec