Revert "Update lib installation path (multiarch portability)."

This reverts commit 0d0fa66c.

src/CMakeLists.txt

@@ -46,14 +46,14 @@ SET_TARGET_PROPERTIES(${LIBRARY_NAME} PROPERTIES SOVERSION ${PROJECT_VERSION})
 PKG_CONFIG_USE_DEPENDENCY(${LIBRARY_NAME} dynamic-graph)
 
 INSTALL(TARGETS ${LIBRARY_NAME}
-  DESTINATION ${CMAKE_INSTALL_LIBDIR})
+  DESTINATION lib)
 
 SET(EXECUTABLE_NAME dg-python)
 ADD_EXECUTABLE(${EXECUTABLE_NAME} dg-python.cc)
 TARGET_LINK_LIBRARIES(${EXECUTABLE_NAME}
   ${LIBRARY_NAME}
   )
-INSTALL(TARGETS dg-python DESTINATION ${CMAKE_INSTALL_BINDIR})
+INSTALL(TARGETS dg-python DESTINATION bin)
 
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