transmission_4: fix build on Darwin

Transmission detects gettext and tries to enable support on Darwin but
fails without this substitution.

Author: reckenrode

pkgs/applications/networking/p2p/transmission/4.nix

@@ -113,6 +113,10 @@ stdenv.mkDerivation (finalAttrs: {
       cmake/FindUtfCpp.cmake
     # Upstream uses different config file name.
     substituteInPlace CMakeLists.txt --replace 'find_package(UtfCpp)' 'find_package(utf8cpp)'
+
+    # Use gettext even on Darwin
+    substituteInPlace libtransmission/utils.h \
+      --replace-fail '#if defined(HAVE_GETTEXT) && !defined(__APPLE__)' '#if defined(HAVE_GETTEXT)'
   '';
 
   nativeBuildInputs = [