haskellPackages.mkDerivation: check haddock availability

This change makes the haskell builder run the haddockPhase only if the
haddock program is availble (for example, it's not when cross-compiling).

pkgs/development/compilers/ghc/8.10.7.nix

@@ -366,6 +366,10 @@ stdenv.mkDerivation (rec {
     inherit llvmPackages;
     inherit enableShared;
 
+    # This is used by the haskell builder to query
+    # the presence of the haddock program.
+    hasHaddock = enableHaddockProgram;
+
     # Our Cabal compiler name
     haskellCompilerName = "ghc-${version}";
   };

pkgs/development/compilers/ghc/8.8.4.nix

@@ -335,6 +335,10 @@ stdenv.mkDerivation (rec {
     inherit llvmPackages;
     inherit enableShared;
 
+    # This is used by the haskell builder to query
+    # the presence of the haddock program.
+    hasHaddock = enableHaddockProgram;
+
     # Our Cabal compiler name
     haskellCompilerName = "ghc-${version}";
   };

pkgs/development/compilers/ghc/9.0.2.nix

@@ -331,6 +331,10 @@ stdenv.mkDerivation (rec {
     inherit llvmPackages;
     inherit enableShared;
 
+    # This is used by the haskell builder to query
+    # the presence of the haddock program.
+    hasHaddock = enableHaddockProgram;
+
     # Our Cabal compiler name
     haskellCompilerName = "ghc-${version}";
   };

pkgs/development/compilers/ghc/9.2.2.nix

@@ -331,6 +331,10 @@ stdenv.mkDerivation (rec {
     inherit llvmPackages;
     inherit enableShared;
 
+    # This is used by the haskell builder to query
+    # the presence of the haddock program.
+    hasHaddock = enableHaddockProgram;
+
     # Our Cabal compiler name
     haskellCompilerName = "ghc-${version}";
   };

pkgs/development/compilers/ghc/head.nix

@@ -347,6 +347,10 @@ stdenv.mkDerivation (rec {
     inherit llvmPackages;
     inherit enableShared;
 
+    # This is used by the haskell builder to query
+    # the presence of the haddock program.
+    hasHaddock = enableHaddockProgram;
+
     # Our Cabal compiler name
     haskellCompilerName = "ghc-${version}";
   };

pkgs/development/haskell-modules/generic-builder.nix

@@ -55,7 +55,7 @@ in
 , changelog ? null
 , mainProgram ? null
 , doCoverage ? false
-, doHaddock ? !(ghc.isHaLVM or false)
+, doHaddock ? !(ghc.isHaLVM or false) && (ghc.hasHaddock or true)
 , doHaddockInterfaces ? doHaddock && lib.versionAtLeast ghc.version "9.0.1"
 , passthru ? {}
 , pkg-configDepends ? [], libraryPkgconfigDepends ? [], executablePkgconfigDepends ? [], testPkgconfigDepends ? [], benchmarkPkgconfigDepends ? []