ghc: Default integer-simple usage based one whether GNU MP is available

The user's choice is still always respected

pkgs/development/compilers/ghc/7.10.3.nix

@@ -16,7 +16,7 @@
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
-  enableIntegerSimple ? false, gmp ? null
+  enableIntegerSimple ? !(gmp.meta.available or false), gmp
 
 , # If enabled, use -fPIC when compiling static libs.
   enableRelocatedStaticLibs ? targetPlatform != hostPlatform
@@ -30,8 +30,6 @@
   ghcFlavour ? stdenv.lib.optionalString (targetPlatform != hostPlatform) "perf-cross"
 }:
 
-assert !enableIntegerSimple -> gmp != null;
-
 let
   inherit (bootPkgs) ghc;
 

pkgs/development/compilers/ghc/8.0.2.nix

@@ -15,7 +15,7 @@
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
-  enableIntegerSimple ? false, gmp ? null
+  enableIntegerSimple ? !(gmp.meta.available or false), gmp
 
 , # If enabled, use -fPIC when compiling static libs.
   enableRelocatedStaticLibs ? targetPlatform != hostPlatform
@@ -29,8 +29,6 @@
   ghcFlavour ? stdenv.lib.optionalString (targetPlatform != hostPlatform) "perf-cross"
 }:
 
-assert !enableIntegerSimple -> gmp != null;
-
 let
   inherit (bootPkgs) ghc;
 

pkgs/development/compilers/ghc/8.2.2.nix

@@ -16,7 +16,7 @@
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
-  enableIntegerSimple ? false, gmp ? null
+  enableIntegerSimple ? !(gmp.meta.available or false), gmp
 
 , # If enabled, use -fPIC when compiling static libs.
   enableRelocatedStaticLibs ? targetPlatform != hostPlatform
@@ -34,8 +34,6 @@
   deterministicProfiling ? false
 }:
 
-assert !enableIntegerSimple -> gmp != null;
-
 let
   inherit (bootPkgs) ghc;
 

pkgs/development/compilers/ghc/8.4.2.nix

@@ -15,7 +15,7 @@
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
-  enableIntegerSimple ? false, gmp ? null
+  enableIntegerSimple ? !(gmp.meta.available or false), gmp
 
 , # If enabled, use -fPIC when compiling static libs.
   enableRelocatedStaticLibs ? targetPlatform != hostPlatform
@@ -32,8 +32,6 @@
   ghcFlavour ? stdenv.lib.optionalString (targetPlatform != hostPlatform) "perf-cross"
 }:
 
-assert !enableIntegerSimple -> gmp != null;
-
 let
   inherit (bootPkgs) ghc;
 

pkgs/development/compilers/ghc/head.nix

@@ -15,7 +15,7 @@
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
-  enableIntegerSimple ? false, gmp ? null
+  enableIntegerSimple ? !(gmp.meta.available or false), gmp
 
 , # If enabled, use -fPIC when compiling static libs.
   enableRelocatedStaticLibs ? targetPlatform != hostPlatform
@@ -33,8 +33,6 @@
   ghcFlavour ? stdenv.lib.optionalString (targetPlatform != hostPlatform) "perf-cross"
 }:
 
-assert !enableIntegerSimple -> gmp != null;
-
 let
   inherit (bootPkgs) ghc;
 

pkgs/development/libraries/gmp/6.x.nix

@@ -75,6 +75,7 @@ let self = stdenv.mkDerivation rec {
          asymptotically faster algorithms.
       '';
 
+    broken = with stdenv.hostPlatform; useAndroidPrebuilt || useiOSPrebuilt;
     platforms = platforms.all;
     maintainers = [ maintainers.peti maintainers.vrthra ];
   };

pkgs/top-level/haskell-packages.nix

@@ -8,7 +8,6 @@ let
   integerSimpleExcludes = [
     "ghc7103Binary"
     "ghc821Binary"
-    "ghcCross"
     "ghcjs"
     "ghcjs710"
     "ghcjs80"