[CMake] Use CMAKE_*_OUTPUT_DIRECTORY variables instead of custom vars

Author: rintaro

CMakeLists.txt

@@ -25,16 +25,13 @@ endif()
 # The subdirectory into which host libraries will be installed.
 set(SWIFT_HOST_LIBRARIES_SUBDIRECTORY "swift/host")
 
-if(SWIFT_HOST_LIBRARIES_DEST_DIR)
-  set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${SWIFT_HOST_LIBRARIES_DEST_DIR}")
-  set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${SWIFT_HOST_LIBRARIES_DEST_DIR}")
-else()
+if(NOT CMAKE_ARCHIVE_OUTPUT_DIRECTORY)
   set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib/${SWIFT_HOST_LIBRARIES_SUBDIRECTORY}")
+endif()
+if(NOT CMAKE_LIBRARY_OUTPUT_DIRECTORY)
   set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib/${SWIFT_HOST_LIBRARIES_SUBDIRECTORY}")
 endif()
-if(SWIFT_HOST_RUNTIME_DEST_DIR)
-  set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${SWIFT_HOST_RUNTIME_DEST_DIR}")
-else()
+if(NOT CMAKE_RUNTIME_OUTPUT_DIRECTORY)
   set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin")
 endif()