fzf: only wrap perl on Linux

As the comment says, this should only have happened on Linux, not all
non-Darwin platforms.

Fixes pkgsCross.x86_64-netbsd.fzf.

Fixes: 1693ed2be9 ("fzf: wrap 'perl' in scripts with LOCALE_ARCHIVE")

pkgs/tools/misc/fzf/default.nix

@@ -17,7 +17,7 @@ let
   # on Linux, wrap perl in the bash completion scripts with the glibc locales,
   # so that using the shell completion (ctrl+r, etc) doesn't result in ugly
   # warnings on non-nixos machines
-  ourPerl = if stdenv.isDarwin then perl else (
+  ourPerl = if !stdenv.isLinux then perl else (
     writeShellScriptBin "perl" ''
       export LOCALE_ARCHIVE="${glibcLocales}/lib/locale/locale-archive"
       exec ${perl}/bin/perl "$@"