flatpak: Add a way to easily run gdb inside the sandbox

4 jobs from master in 75 minutes and 23 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Docker Image
passed #91172
pitivi:1.0

00:51:11

passed #91171
pitivi:master

01:02:25

 
  Build
passed #91173
build

00:07:19

 
  Test Results
passed #91174
test-results

00:05:38