Add detection of lib/lib64 directory

CMakeLists.txt

@@ -169,6 +169,36 @@ elseif(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX)
 	endif()
 endif()
 
+
+if(NOT DEFINED CMAKE_INSTALL_LIBDIR)
+  set(_LIBDIR_DEFAULT "lib")
+  # Override this default 'lib' with 'lib64' iff:
+  #  - we are on Linux system but NOT cross-compiling
+  #  - we are NOT on debian
+  #  - we are on a 64 bits system
+  # reason is: amd64 ABI: http://www.x86-64.org/documentation/abi.pdf
+  # Note that the future of multi-arch handling may be even
+  # more complicated than that: http://wiki.debian.org/Multiarch
+  if(CMAKE_SYSTEM_NAME MATCHES "Linux"
+      AND NOT CMAKE_CROSSCOMPILING
+      AND NOT EXISTS "/etc/debian_version")
+    if(NOT DEFINED CMAKE_SIZEOF_VOID_P)
+      message(AUTHOR_WARNING
+        "Unable to determine default CMAKE_INSTALL_LIBDIR directory because no target architecture is known. "
+        "Please enable at least one language before including GNUInstallDirs.")
+    else()
+      if("${CMAKE_SIZEOF_VOID_P}" EQUAL "8")
+        set(_LIBDIR_DEFAULT "lib64")
+      endif()
+    endif()
+  endif()
+  set(CMAKE_INSTALL_LIBDIR "${_LIBDIR_DEFAULT}" CACHE PATH "object code libraries (${_LIBDIR_DEFAULT})")
+endif()
+
+SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}")
+SET(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
+#SET(CMAKE_MACOSX_RPATH ON)
+
 #-- generate library headers
 configure_file( ${CMAKE_SOURCE_DIR}/include/SFCGAL/config.h.cmake ${CMAKE_SOURCE_DIR}/include/SFCGAL/config.h )
 configure_file( ${CMAKE_SOURCE_DIR}/include/SFCGAL/version.h.cmake ${CMAKE_SOURCE_DIR}/include/SFCGAL/version.h )

sfcgal-config.in

@@ -1,6 +1,6 @@
 #!/bin/sh
 prefix=@CMAKE_INSTALL_PREFIX@
-libdir=${prefix}/lib
+libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
 
 usage()
 {