libmcrypt: fix build with gcc14

Author: mweinelt

pkgs/by-name/li/libmcrypt/package.nix

@@ -25,9 +25,10 @@ stdenv.mkDerivation rec {
       "ac_cv_func_realloc_0_nonnull=yes"
     ];
 
-  env = lib.optionalAttrs stdenv.cc.isClang {
-    NIX_CFLAGS_COMPILE = "-Wno-implicit-function-declaration -Wno-implicit-int";
-  };
+  env.NIX_CFLAGS_COMPILE = toString [
+    "-Wno-implicit-function-declaration"
+    "-Wno-implicit-int"
+  ];
 
   meta = {
     description = "Replacement for the old crypt() package and crypt(1) command, with extensions";