runzip: fix build

Configure script produces a cryptic message:

```
configure:4540: error: ZLIB version too old, please install at least v1.1.2
```

It's actually misleading and comes from the vendored libzip 0.7.1 configure check.
It fails due to do `-Wimplicit-int`:

```
conftest.c:16:16: error: type defaults to 'int' in declaration of 'unzOpen' [-Wimplicit-int]
   16 | extern ZEXPORT unzOpen (const char *path);
```

Vendored libzip is pretty heavily modified and unvendoring seems impossible.
Furthermore, libzip from nixpkgs in buildInputs
is actually unused and can be dropped - only zlib is necessary.

pkgs/by-name/ru/runzip/package.nix

@@ -2,8 +2,8 @@
   lib,
   stdenv,
   fetchFromGitHub,
-  libzip,
   libiconv,
+  zlib,
   autoreconfHook,
 }:
 
@@ -14,7 +14,7 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ autoreconfHook ];
   buildInputs = [
     libiconv
-    libzip
+    zlib
   ];
 
   src = fetchFromGitHub {
@@ -24,6 +24,11 @@ stdenv.mkDerivation rec {
     sha256 = "0l5zbb5hswxczigvyal877j0aiq3fc01j3gv88bvy7ikyvw3lc07";
   };
 
+  env.NIX_CFLAGS_COMPILE = toString [
+    "-Wno-error=implicit-int"
+    "-Wno-error=incompatible-pointer-types"
+  ];
+
   meta = {
     description = "Tool to convert filename encoding inside a ZIP archive";
     license = lib.licenses.bsd2;