tests: skip test if specific spa lib is not installed

Avoids tests failing if pipewire was built without the spa lib
7 jobs for test-skip-if-not-installed in 1 minute and 18 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Container
passed container_fedora #11939192

00:00:14

passed container_ubuntu #11939193

00:00:15

 
  Build
passed build_on_fedora_no_docs #11939195

00:00:58

passed build_on_fedora_with_docs #11939194

00:01:02

passed build_on_fedora_wpipc #11939196

00:00:58

passed build_on_ubuntu_no_gir #11939198

00:00:58

passed build_on_ubuntu_with_gir #11939197

00:00:38