"Make Installed Build" rebuild all after interrupt

I am try to create Installed Build for Linux.

I use bash script

./release/Engine/Build/BatchFiles/RunUAT.sh BuildGraph \
    -script=Engine/Build/InstalledEngineBuild.xml \
    -target="Make Installed Build Linux" \
    -set:WithClient=true \
    -set:WithServer=true \
    -set:BuiltDirectory=$HOME/bin/ue-release \
    -set:HostPlatformOnly=true 

Some time i need to interrupt build process for power off my PC.
I run build script again after power on.

Question:
Why build tool rebuild all after interrupt?
It is waste my time =\