libmemcached: fix linking with libpthread

Add patch to fix linking against libpthread (from Fedora).

https://bugzilla.redhat.com/show_bug.cgi?id=1037707
https://bugs.launchpad.net/libmemcached/+bug/1281907

This fixes (upcoming) libmemcached use in collectd, which currently
doesn't work because of link failure caused by missing "pthread_once"
symbol.

pkgs/development/libraries/libmemcached/default.nix

@@ -8,6 +8,11 @@ stdenv.mkDerivation rec {
     sha256 = "10jzi14j32lpq0if0p9vygcl2c1352hwbywzvr9qzq7x6aq0nb72";
   };
   
+  # Fix linking against libpthread (patch from Fedora)
+  # https://bugzilla.redhat.com/show_bug.cgi?id=1037707
+  # https://bugs.launchpad.net/libmemcached/+bug/1281907
+  patches = [ ./libmemcached-fix-linking-with-libpthread.patch ];
+
   buildInputs = [ cyrus_sasl libevent ];
 
   meta = {

pkgs/development/libraries/libmemcached/libmemcached-fix-linking-with-libpthread.patch

@@ -0,0 +1,19 @@
+diff -up libmemcached-1.0.16/build-aux/ltmain.sh.orig libmemcached-1.0.16/build-aux/ltmain.sh
+--- libmemcached-1.0.16/build-aux/ltmain.sh.orig	2013-12-03 16:36:53.222107642 +0100
++++ libmemcached-1.0.16/build-aux/ltmain.sh	2013-12-03 16:37:35.770132249 +0100
+@@ -5664,6 +5664,15 @@ func_mode_link ()
+ 	    *" $arg "*) ;;
+ 	    * ) func_append new_inherited_linker_flags " $arg" ;;
+ 	esac
++	# As we are forced to pass -nostdlib to g++ during linking, the option
++	# -pthread{,s} is not in effect;  add the -lpthread to $deplist
++	# explicitly to link correctly.
++	if test "$tagname" = CXX -a x"$with_gcc" = xyes; then
++	  case "$arg" in
++	    -pthread*) func_append deplibs " -lpthread" ;;
++	  esac
++	fi
++
+ 	continue
+ 	;;
+