Source: upstream r1153602
Index: a/cmake/modules/SIPMacros.cmake
===================================================================
--- a/cmake/modules/SIPMacros.cmake	(revision 1153601)
+++ b/cmake/modules/SIPMacros.cmake	(revision 1153602)
@@ -119,6 +119,6 @@
     TARGET_LINK_LIBRARIES(${_logical_name} ${EXTRA_LINK_LIBRARIES})
     SET_TARGET_PROPERTIES(${_logical_name} PROPERTIES PREFIX "" OUTPUT_NAME ${_child_module_name})
 
-    INSTALL(TARGETS ${_logical_name} DESTINATION "${PYTHON_SITE_PACKAGES_DIR}/${_parent_module_path}")
+    INSTALL(TARGETS ${_logical_name} DESTINATION "${PYTHON_SITE_PACKAGES_INSTALL_DIR}/${_parent_module_path}")
 
 ENDMACRO(ADD_SIP_PYTHON_MODULE)