opencl.bst: load ICD files only from %{libdir}/GL

With Mesa being an extension, this is the only directory expected to
contain ICD files.
8 jobs for doraskayo/fix-icd-path in 97 minutes and 14 seconds (queued for 1 second)
Status Job ID Name Coverage
  Flatpak
passed #219290234
aarch64
app_aarch64

01:34:08

passed #219290236
armhf
app_arm

00:43:55

passed #219290233
cache_i686 x86_64
app_i686

00:58:04

passed #219290232
cache_x86_64 x86_64
app_x86_64

00:57:24

 
  Vm
manual #219290240
aarch64 allowed to fail manual
minimal_systemd_vm_aarch64
passed #219290241
armhf
minimal_systemd_vm_arm

00:03:03

passed #219290239
cache_i686 x86_64
minimal_systemd_vm_i686

00:01:44

passed #219290237
cache_x86_64 x86_64
minimal_systemd_vm_x86_64

00:01:36