simbaplusplus: add missing python to checkInputs

Required for checks, see https://github.com/pgarba/SiMBA-/blob/64be925af27387b912cf159fbce3392f767a03c9/CMakeLists.txt#L124-L140

pkgs/by-name/si/simbaplusplus/package.nix

@@ -5,6 +5,7 @@
   cmake,
   llvmPackages,
   z3,
+  python3,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -33,6 +34,10 @@ stdenv.mkDerivation (finalAttrs: {
     z3
   ];
 
+  checkInputs = [
+    python3
+  ];
+
   doCheck = true;
 
   meta = {