Add instructions on using go with admin perms
Add instructions on using go with admin perms

For testing and possibly other operations go might need elevated
permissions. Some parts of documentation and the BUILDING.md mention
using `sudo go` but does not explain how to achieve this. This commit
inserts instructions to the BUILDING.md as a small note. Note mentions
systemwide and local solutions.

Signed-off-by: Mete Durlu <12ca25b200615c264be8cf239e82bec3b1ff01d7@ibm.com>

containerd/containerd,dmcgowan/containerd,dmcgowan/containerd,estesp/containerd,mikebrow/containerd,thaJeztah/containerd,estesp/containerd,mikebrow/containerd,thaJeztah/containerd,containerd/containerd