Tell hadrian to use hashes in unit ids

Author: andreabedini

compiler/ghc/default.nix

@@ -331,8 +331,10 @@ let
       # iPhones/iPads/... won't understand the compiled code, as the compiler will emit LDSETALH
       # + lib.optionalString (targetPlatform.???) "'*.rts.ghc.c.opts += -optc-mcpu=apple-a7 -optc-march=armv8-a+norcpc'"
       # For GHC versions in the 9.x range that don't support the +native_bignum flavour transformer yet
-      + lib.optionalString ((enableNativeBignum && !hadrianHasNativeBignumFlavour))
+      + lib.optionalString (enableNativeBignum && !hadrianHasNativeBignumFlavour)
         " --bignum=native"
+      # Tell hadrian to hash the unit-ids
+      + lib.optionalString (builtins.compareVersions ghc-version "9.8" >= 0) " --hash-unit-ids"
       ;
 
   # When installation is done by copying the stage1 output the directory layout