haskell.compiler.ghc901: build using ghc8102BinaryMinimal on arm

ghc8102Binary doesn't build on hydra on arm since it exceeds the maximum
output size. This change works around this issue by using the minimal
version of that compiler instead.

pkgs/top-level/haskell-packages.nix

@@ -76,7 +76,11 @@ in {
       llvmPackages = pkgs.llvmPackages_9;
     };
     ghc901 = callPackage ../development/compilers/ghc/9.0.1.nix {
-      bootPkgs = packages.ghc8102Binary;
+      # aarch64 ghc8102Binary exceeds max output size on hydra
+      bootPkgs = if stdenv.isAarch64 || stdenv.isAarch32 then
+          packages.ghc8102BinaryMinimal
+        else
+          packages.ghc8102Binary;
       inherit (buildPackages.python3Packages) sphinx;
       buildLlvmPackages = buildPackages.llvmPackages_10;
       llvmPackages = pkgs.llvmPackages_10;