clang: remove suffix from clang completion

Ideally we'd do this at another layer.

Fixes #1416
2 jobs for master in 58 minutes and 24 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed flatpak #1208235
flatpak

00:54:24

 
  Deploy
passed nightly #1208236

00:04:00