From: Jonathan Riddell <jriddell@ubuntu.com>
Subject: Add multiarch lib path support to find_library() (HACK)
Bug: http://public.kitware.com/Bug/view.php?id=12037
Bug-Debian: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=618932
Bug-Ubuntu: https://bugs.launchpad.net/debian/+source/cmake/+bug/737137
Origin: vendor, http://bugs.debian.org/cgi-bin/bugreport.cgi?msg=5;filename=ubuntu_multiarch_library_directory.diff;att=1;bug=618932
Forwarded: yes
Acked-By: Modestas Vainius <modax@debian.org>
Last-Update: 2011-06-07

This is the same as ubuntu_multiarch_library_directory.diff in Ubuntu packages.
I do not consider this patch to be a proper fix but rather hack-level stuff.
It does not support cross-compilation or find_package() etc. However, the lack
of better solution at the right time forced me to include it.  Hopefully, it's
temporary.

--- a/Modules/Platform/UnixPaths.cmake
+++ b/Modules/Platform/UnixPaths.cmake
@@ -29,6 +29,8 @@ SET(UNIX 1)
 GET_FILENAME_COMPONENT(_CMAKE_INSTALL_DIR "${CMAKE_ROOT}" PATH)
 GET_FILENAME_COMPONENT(_CMAKE_INSTALL_DIR "${_CMAKE_INSTALL_DIR}" PATH)
 
+EXECUTE_PROCESS(COMMAND dpkg-architecture -qDEB_HOST_MULTIARCH OUTPUT_VARIABLE CMAKE_ARCH_TRIPLET OUTPUT_STRIP_TRAILING_WHITESPACE)
+
 # List common installation prefixes.  These will be used for all
 # search types.
 LIST(APPEND CMAKE_SYSTEM_PREFIX_PATH
@@ -74,6 +76,7 @@ LIST(APPEND CMAKE_SYSTEM_PROGRAM_PATH
   )
 
 LIST(APPEND CMAKE_PLATFORM_IMPLICIT_LINK_DIRECTORIES
+  /lib/${CMAKE_ARCH_TRIPLET} /usr/lib/${CMAKE_ARCH_TRIPLET}
   /lib /usr/lib /usr/lib32 /usr/lib64
   )
 
--- a/Source/cmFindBase.cxx
+++ b/Source/cmFindBase.cxx
@@ -346,6 +346,14 @@ void cmFindBase::AddPrefixPaths(std::vec
       {
       dir += "/";
       }
+    if (subdir == "lib")
+      {
+      const char* triplet = this->Makefile->GetDefinition("CMAKE_ARCH_TRIPLET");
+      if (triplet)
+        {
+        this->AddPathInternal(dir+"lib/"+triplet, pathType);
+        }
+      }
     std::string add = dir + subdir;
     if(add != "/")
       {