Add haskell.lib.setBuiltTarget, and support non library compiling of a single target

pkgs/test/haskell/default.nix

@@ -3,4 +3,5 @@
 lib.recurseIntoAttrs {
   shellFor = callPackage ./shellFor { };
   documentationTarball = callPackage ./documentationTarball { };
+  setBuildTarget = callPackage ./setBuildTarget { };
 }

pkgs/test/haskell/setBuildTarget/Bar.hs

@@ -0,0 +1,4 @@
+module Main where
+
+main :: IO ()
+main = putStrLn "Hello, Bar!"

pkgs/test/haskell/setBuildTarget/Foo.hs

@@ -0,0 +1,4 @@
+module Main where
+
+main :: IO ()
+main = putStrLn "Hello, Foo!"

pkgs/test/haskell/setBuildTarget/Setup.hs

@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain

pkgs/test/haskell/setBuildTarget/default.nix

@@ -0,0 +1,26 @@
+{ pkgs, haskellPackages }: with pkgs.haskell.lib;
+
+
+let
+  drv     = haskellPackages.callCabal2nix "haskell-setBuildTarget" ./. {};
+  test    = target: excluded:
+
+    let only = setBuildTarget drv target;
+    in ''
+         if [[ ! -f "${only}/bin/${target}" ]]; then
+           echo "${target} was not built"
+           exit 1
+         fi
+
+         if [[ -f "${only}/bin/${excluded}" ]]; then
+           echo "${excluded} was built, when it should not have been"
+           exit 1
+         fi
+     '';
+
+in pkgs.runCommand "test haskell.lib.setBuildTarget" {} ''
+  ${test "foo" "bar"}
+  ${test "bar" "foo"}
+  touch "$out"
+''
+

pkgs/test/haskell/setBuildTarget/haskell-setBuildTarget.cabal

@@ -0,0 +1,16 @@
+cabal-version:       >=1.10
+name:                haskell-setBuildTarget
+version:             0.1.0.0
+author:              Isaac Shapira
+maintainer:          fresheyeball@protonmail.com
+build-type:          Simple
+
+executable foo
+  main-is:             Foo.hs
+  build-depends:       base
+  default-language:    Haskell2010
+
+executable bar
+  main-is:             Bar.hs
+  build-depends:       base
+  default-language:    Haskell2010