Install procps

Author: cgrindel

rules_haskell_tests/shell.nix

@@ -38,7 +38,7 @@ mkShell {
     file
   ] ++ lib.optionals docTools [ graphviz python39Packages.sphinx zip unzip ];
 
-  packages = [ bazel_6 ];
+  packages = [ bazel_6 procps ];
 
   shellHook = ''
     # Add nix config flags to .bazelrc.local.