Honor CMAKE_INSTALL_***DIR variables

Author: tristanlabelle

CMakeLists.txt

@@ -117,12 +117,12 @@ endif()
 set_property(GLOBAL APPEND PROPERTY XCTest_EXPORTS XCTest)
 get_swift_host_arch(swift_arch)
 install(TARGETS XCTest
-  ARCHIVE DESTINATION lib/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>
-  LIBRARY DESTINATION lib/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>
-  RUNTIME DESTINATION bin)
+  ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>
+  LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>
+  RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 install(FILES
   ${CMAKE_CURRENT_BINARY_DIR}/swift/XCTest.swiftdoc
   ${CMAKE_CURRENT_BINARY_DIR}/swift/XCTest.swiftmodule
-  DESTINATION lib/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>/${swift_arch})
+  DESTINATION ${CMAKE_INSTALL_LIBDIR}/swift$<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:_static>/$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>/${swift_arch})
 
 add_subdirectory(cmake/modules)