cmake: Install libraries according to multi-arch rules

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit 88e7ccc716)

CMakeLists.txt

@@ -31,6 +31,7 @@ include( CheckIncludeFile       )
 include( CheckLibraryExists     )
 include( CheckCSourceCompiles   )
 include( CheckCXXSourceCompiles )
+include( GNUInstallDirs OPTIONAL )
 
 
 ##### include our cmake modules
@@ -43,7 +44,11 @@ include( TDEMacros )
 
 tde_setup_install_path( EXEC_INSTALL_PREFIX "${CMAKE_INSTALL_PREFIX}" )
 tde_setup_install_path( BIN_INSTALL_DIR     "${EXEC_INSTALL_PREFIX}/bin" )
-tde_setup_install_path( LIB_INSTALL_DIR     "${EXEC_INSTALL_PREFIX}/lib${LIB_SUFFIX}" )
+if( CMAKE_INSTALL_LIBDIR )
+  tde_setup_install_path( LIB_INSTALL_DIR   "${EXEC_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}" )
+else( )
+  tde_setup_install_path( LIB_INSTALL_DIR   "${EXEC_INSTALL_PREFIX}/lib${LIB_SUFFIX}" )
+endif( )
 
 tde_setup_install_path( INCLUDE_INSTALL_DIR   "${CMAKE_INSTALL_PREFIX}/include/tqt" )
 tde_setup_install_path( PKGCONFIG_INSTALL_DIR "${LIB_INSTALL_DIR}/pkgconfig" )