nph: Fix nph -v

Would previously fail with:

```shell
> nph -v
/bin/sh: git: not found
```

Now it can show 0.6.1 correctly.

Signed-off-by: Daniel Schaefer <git@danielschaefer.me>

pkgs/by-name/np/nph/package.nix

@@ -10,10 +10,15 @@ let
     nim2 = nim-2_0;
   };
 in
-buildNimPackage' (finalAttrs: {
+buildNimPackage' (finalAttrs: rec {
   pname = "nph";
   version = "0.6.1";
 
+  postPatch = ''
+    substituteInPlace src/nph.nim \
+      --replace-fail 'git describe --long --dirty --always --tags' "echo ${version}"
+  '';
+
   src = fetchFromGitHub {
     owner = "arnetheduck";
     repo = "nph";