Add -j4 to limit how many cores is used to build ffmpeg-ios binaries.
Error in logs: "posix_spawn failed: Resource temporarily unavailable"
Task-number: QTQAINFRA-6803
Pick-to: 6.8
Change-Id: I3fb56cdbe4cbda8f779852b0a16121916aa5a1d4
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>
Reviewed-by: Jukka Jokiniva <jukka.jokiniva@qt.io>
(cherry picked from commit 6569f201c1)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
b7abace894