Fix finding Vulkan explicit layers from GL extensions

Fixes #862.
10 jobs for valentindavid/mesa-vulkan-layers-19.08 in 223 minutes and 11 seconds
Status Job ID Name Coverage
  Flatpak
passed #294473369
aarch64
app_aarch64

03:40:41

passed #294473370
armhf
app_arm

01:20:49

passed #294473367
cache_i686 x86_64
app_i686

01:53:45

passed #294473371
ppc64le allowed to fail
app_powerpc64le

01:38:55

passed #294473366
cache_x86_64 x86_64
app_x86_64

01:48:41

 
  Vm
manual #294473375
aarch64 allowed to fail manual
minimal_systemd_vm_aarch64
passed #294473376
armhf
minimal_systemd_vm_arm

00:02:30

passed #294473374
cache_i686 x86_64
minimal_systemd_vm_i686

00:01:44

manual #294473377
ppc64le allowed to fail manual
minimal_systemd_vm_powerpc64le
passed #294473372
cache_x86_64 x86_64
minimal_systemd_vm_x86_64

00:01:27