builds fail outside of git tree in CentOS.
Reproduced in 18.10:
Steps to reproduce:
git checkout v18.10
cd vpp
make install-dep
make dist
...in a clean directory
xz -dc /home/therbert/vpp/build-root/vpp-18.10-release.tar.xz | /usr/bin/tar -xf -
cd vpp-18.10
make build-release
Output is attached.