Don't need to run previous iterations commands again

Summary: BUG: 393141

Test Plan:
Tested building plasma-workspace, it was clearly faster (although it
would have finished eventually)

Reviewers: Frameworks, arojas, sitter

Reviewed By: sitter

Subscribers: sitter, heikobecker

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D12216