sage: make it possible not to rebuild sage-tests

Requiring sage-tests as build input just so it gets build is a bit
unfortunatey but understandable. This commit introduces an option to not
add sage-tests as a dependency. This is preferred in case e.g. Python
packages are added to the environment.

pkgs/applications/science/math/sage/default.nix

@@ -1,5 +1,6 @@
 { pkgs
 , withDoc ? false
+, requireSageTests ? true
 , extraPythonPackages ? ps: []
 }:
 
@@ -167,5 +168,5 @@ in
 # A wrapper around sage that makes sure sage finds its docs (if they were build).
 callPackage ./sage.nix {
   inherit sage-tests sage-with-env sagedoc jupyter-kernel-definition;
-  inherit withDoc;
+  inherit withDoc requireSageTests;
 }

pkgs/applications/science/math/sage/sage.nix

@@ -6,6 +6,7 @@
 , jupyter-kernel
 , sagedoc
 , withDoc
+, requireSageTests
 }:
 
 # A wrapper that makes sure sage finds its docs (if they were build) and the
@@ -26,7 +27,7 @@ stdenv.mkDerivation rec {
 
   buildInputs = [
     makeWrapper
-
+  ] ++ lib.optionals requireSageTests [
     # This is a hack to make sure sage-tests is evaluated. It doesn't acutally
     # produce anything of value, it just decouples the tests from the build.
     sage-tests