Commit f2d1accf authored by Leon Schoorl's avatar Leon Schoorl Committed by Marge Bot

Fix GHC_STAGE definition generated by make

Fixes #18070

GHC_STAGE is the stage of the compiler we're building, it should be 1,2(,3?).
But make was generating 0 and 1.

Hadrian does this correctly using a similar `+ 1`:
parent 22641742
Pipeline #22986 failed with stages
in 3 minutes and 17 seconds