[beta] ci: Fix broken link in `build-powerpc64le-toolchain.sh` #45744

Merged

bors merged 1 commit intorust-lang:betafrom

kennytm:centos-vault-beta

Nov 5, 2017

Commits on Nov 3, 2017

Change powerpc64le's Centos base URL to vault.centos.org.
kennytm
committed