cvise: use /bin.bash from nix store

Noticed failures as an incorrect handling of `--command` param:

    $ cvise --command="gcc -c bug.c |& fgrep 'during RTL pass: expand'" bug.c
    C-Vise cannot run because the interestingness test does not return
    zero.

This happens because temporary shell script has "#!/bin/bash" shebang.

The change replaces it to path from nix store.

pkgs/development/tools/misc/cvise/default.nix

@@ -1,4 +1,4 @@
-{ lib, buildPythonApplication, fetchFromGitHub, cmake, flex
+{ lib, buildPythonApplication, fetchFromGitHub, bash, cmake, flex
 , libclang, llvm, unifdef
 , pebble, psutil, pytestCheckHook, pytest-flake8
 }:
@@ -20,10 +20,16 @@ buildPythonApplication rec {
   ];
 
   nativeBuildInputs = [ cmake flex llvm.dev ];
-  buildInputs = [ libclang llvm llvm.dev unifdef ];
+  buildInputs = [ bash libclang llvm llvm.dev unifdef ];
   propagatedBuildInputs = [ pebble psutil ];
   checkInputs = [ pytestCheckHook pytest-flake8 unifdef ];
 
+  # 'cvise --command=...' generates a script with hardcoded shebang.
+  postPatch = ''
+    substituteInPlace cvise.py \
+      --replace "#!/bin/bash" "#!${bash}/bin/bash"
+  '';
+
   preCheck = ''
     patchShebangs cvise.py
   '';