cmake-server: Normalize build and source directories

Fixes: #18862
17 jobs for 18862-normalize-server-mode-paths
Status Job ID Name Coverage
  External
passed cdash

passed cmake-dash3win7-windows-release-ninja

passed cmake-moonshade-osx-debug-ninja

passed ghostflow-check-master

passed ghostflow-stager

passed cmake-dash3win7-windows-release-ninja

passed cmake-dash3win7-windows-release-ninja

passed cmake-dash3win7-windows-release-ninja

00:26:54

passed cmake-dash3win7-windows-release-ninja

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-debug-ninja

passed cmake-moonshade-osx-debug-ninja

00:13:45

passed cmake-moonshade-osx-debug-ninja

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager

passed ghostflow-stager