libgphoto2: fix build on macOS

We remove `libgphoto2` from its own package.nix inputs (it is an
unused argument) and move `gettext` from nativeBuildInputs to
buildInputs, since `libgphoto2` links against it.

pkgs/by-name/li/libgphoto2/package.nix

@@ -9,7 +9,6 @@
   libusb1,
   libtool,
   libexif,
-  libgphoto2,
   libjpeg,
   curl,
   libxml2,
@@ -31,21 +30,18 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [
     autoreconfHook
-    gettext
     libtool
     pkg-config
   ];
 
   buildInputs = [
+    gettext
     libjpeg
     libtool # for libltdl
     libusb1
     curl
     libxml2
     gd
-  ]
-  ++ lib.optionals stdenv.hostPlatform.isDarwin [
-    gettext
   ];
 
   doInstallCheck = true;