cerbero: Keep RSP files when building on Windows

This helps debug build issues since you need to look at the contents
of RSP files to see the actual arguments list, and they're
automatically deleted by default.
3 jobs for keep-rspfiles in 51 minutes and 56 seconds (queued for 1 minute and 13 seconds)
Status Job ID Name Coverage
  Preparation
passed manifest #63476

00:00:19

 
  Build
passed cerbero deps fedora x86_64 #63477

00:40:25

 
  Full Builds
passed build cerbero fedora x86_64 #63478

00:11:10