cmake: Install libraries according to multi-arch rules.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

CMakeLists.txt

@@ -25,6 +25,7 @@ include( CheckSymbolExists      )
 include( CheckIncludeFile       )
 include( CheckLibraryExists     )
 include( CheckCSourceCompiles   )
+include( GNUInstallDirs OPTIONAL )
 
 
 #### include our cmake modules
@@ -35,6 +36,10 @@ include( TDEMacros )
 
 ##### setup install paths
 
+if( CMAKE_INSTALL_LIBDIR )
+  tde_setup_install_path( LIB_INSTALL_DIR "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}" )
+endif( )
+
 include( TDESetupPaths )
 tde_setup_paths( )