Hadrian stage 1 rebuild on --freeze1

Summary

hadrian rebuilds stage1 even on freeze1

Steps to reproduce

git checkout 4c8a67a4b025774993b80442fb3654c8868c1d24
 hadrian/build.stack.sh -j --flavour=quickest
wget https://gist.githubusercontent.com/reactormonk/6e9a02661ec103c8ea94d3ce34082f4e/raw/d27ad4edab9506a263b7fe1c07f0a5074e1baef6/ghc.diff -O ghc.diff
git apply ghc.diff
 hadrian/build.stack.sh test -j --flavour=quickest --freeze1

Expected behavior

No rebuild of stage 1

Environment

GHC version used: 4c8a67a4

Optional:

Operating System: Linux
System Architecture: 64bit

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