make-test-runtime: Look in /{usr/,}sbin for ldconfig

Under normal circumstances ldconfig isn't required to be in ordinary
users' PATHs, but running this script is not a normal circumstance.

Signed-off-by: Simon McVittie <smcv@collabora.com>

Closes: #1630
Approved by: alexlarsson
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f