unzip: fix configure script when using clang 16

Clang 16 makes implicit int and function declarations an error by
default in any mode except for C89. The configure script has two of
these that cause it to misdetect features when using Clang 16.

* Implicit `int main` in the errno check. This is fixed by adding the
missing `int`.
* Implicit definitions of `opendir` and `closedir`. These are fixed by
including the required headers.

pkgs/tools/archivers/unzip/default.nix

···
       ];
       sha256 = "sha256-on79jElQ+z2ULWAq14RpluAqr9d6itHiZwDkKubBzTc=";
     })
+    # Clang 16 makes implicit declarations an error by default for C99 and newer, causing the
+    # configure script to fail to detect errno and the directory libraries on Darwin.
+    ./implicit-declarations-fix.patch
   ] ++ lib.optional enableNLS
     (fetchurl {
       url = "https://gitweb.gentoo.org/repo/gentoo.git/plain/app-arch/unzip/files/unzip-6.0-natspec.patch?id=56bd759df1d0c750a065b8c845e93d5dfa6b549d";
       name = "unzip-6.0-natspec.patch";
       sha256 = "67ab260ae6adf8e7c5eda2d1d7846929b43562943ec4aff629bd7018954058b1";
     });
+
 
   nativeBuildInputs = [ bzip2 ];
   buildInputs = [ bzip2 ] ++ lib.optional enableNLS libnatspec;

pkgs/tools/archivers/unzip/implicit-declarations-fix.patch

···
+--- a/unix/configure	2009-04-16 15:25:12.000000000 -0400
++++ b/unix/configure	2023-05-30 15:18:33.670321348 -0400
+@@ -408,7 +408,7 @@
+ echo Check for errno declaration
+ cat > conftest.c << _EOF_
+ #include <errno.h>
+-main()
++int main()
+ {
+   errno = 0;
+   return 0;
+@@ -419,6 +419,8 @@
+ 
+ echo Check for directory libraries
+ cat > conftest.c << _EOF_
++#include <sys/types.h>
++#include <dirent.h>
+ int main() { return closedir(opendir(".")); }
+ _EOF_
+ 
+