ci: build_changed_aports: Don't exit prematurely if pkg list is empty (MR 5684)

This should check for packages in other repos that need to be built,
even if the main repo pkg list is empty.

fixes !5576

.ci/lib/build_changed_aports.py

@@ -101,11 +101,10 @@ if __name__ == "__main__":
     # No packages: skip build
     if len(packages) == 0:
         print(f"no packages changed, which can be built for {arch}")
-        sys.exit(0)
-
-    # Build packages
-    print(f"building in strict mode for {arch}: {', '.join(packages)}")
-    build_strict(packages, arch)
+    else:
+        # Build packages
+        print(f"building in strict mode for {arch}: {', '.join(packages)}")
+        build_strict(packages, arch)
 
     # Build packages in extra-repos/systemd
     # FIXME: this should probably be more generic, if other repos are added later?