clang: add some stubs for valgrind testing

1 job for master in 10 minutes and 59 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #26060
flatpak

00:10:59

 
Name Stage Failure
failed
flatpak Test
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Building module flatpak in /builds/GNOME/gnome-builder/.flatpak-builder/build/flatpak-1
========================================================================
Already on 'master'
Cloning into '/builds/GNOME/gnome-builder/.flatpak-builder/build/flatpak-1/libglnx'...
error: Server does not allow request for unadvertised object 5362f6bc3ff3e30f379e767b203d15c9e56d6f08
Fetched in submodule path 'libglnx', but it did not contain 5362f6bc3ff3e30f379e767b203d15c9e56d6f08. Direct fetching of that commit failed.
Error: module flatpak: Child process exited with code 1
ERROR: Job failed: exit code 1