diagrams-builder: wrap all available backend executables

This way, we no longer need to track what backends we expect to be
enabled which the diagrams-builder wrapper derivation doesn't
control.

pkgs/tools/graphics/diagrams-builder/default.nix

@@ -25,18 +25,26 @@ let
   wrappedGhc = ghcWithPackages (self: [ diagrams-builder ] ++ extraPackages self);
   ghc = lib.getExe' wrappedGhc "ghc";
 
-  exeWrapper = backend: ''
-    makeWrapper \
-    "${diagrams-builder}/bin/diagrams-builder-${backend}" "$out/bin/diagrams-builder-${backend}" \
-      --set NIX_GHC ${ghc} \
-      --set NIX_GHC_LIBDIR "$(${ghc} --print-libdir)"
-  '';
+  exeWrapper =
+    backend:
+    let
+      exe = "${diagrams-builder}/bin/diagrams-builder-${backend}";
+    in
+    ''
+      test ! -x "${exe}" || \
+      makeWrapper "${exe}" \
+      "$out/bin/diagrams-builder-${backend}" \
+        --set NIX_GHC ${ghc} \
+        --set NIX_GHC_LIBDIR "$(${ghc} --print-libdir)"
+    '';
 
-  backends = [
+  # Needs to match executable, suffix, not flag name
+  allBackends = [
     "svg"
     "ps"
-    # See ../../../development/haskell-modules/configuration-common.nix:/diagrams-builder.=
-    # "cairo"
+    "cairo"
+    "rasterific"
+    "pgf"
   ];
 
 in
@@ -46,7 +54,7 @@ stdenv.mkDerivation {
 
   nativeBuildInputs = [ makeWrapper ];
 
-  buildCommand = lib.concatStringsSep "\n" (map exeWrapper backends);
+  buildCommand = lib.concatStringsSep "\n" (map exeWrapper allBackends);
 
   # Will be faster to build the wrapper locally then to fetch it from a binary cache.
   preferLocalBuild = true;