samtools: Fix cross-compilation

Tests require bgzip which comes from the htslib package.

This did not cause problems prior to
41485e7337 as tests were not run in
cross-compilation.

pkgs/applications/science/biology/samtools/default.nix

@@ -18,6 +18,9 @@ stdenv.mkDerivation rec {
     })
   ];
 
+  # tests require `bgzip` from the htslib package
+  checkInputs = [ htslib ];
+
   nativeBuildInputs = [ perl ];
 
   buildInputs = [ zlib ncurses htslib ];