CMake: De-duplicate references to license file

CMakeCPack.cmake

@@ -14,10 +14,10 @@ if(CMake_INSTALL_DEPENDENCIES)
   include(${CMake_SOURCE_DIR}/Modules/InstallRequiredSystemLibraries.cmake)
 endif()
 
+set(CPACK_RESOURCE_FILE_LICENSE "${CMake_LICENSE_FILE}")
 set(CPACK_PACKAGE_DESCRIPTION_SUMMARY "CMake is a build tool")
 set(CPACK_PACKAGE_VENDOR "Kitware")
-set(CPACK_PACKAGE_DESCRIPTION_FILE "${CMAKE_CURRENT_SOURCE_DIR}/Copyright.txt")
-set(CPACK_RESOURCE_FILE_LICENSE "${CMAKE_CURRENT_SOURCE_DIR}/Copyright.txt")
+set(CPACK_PACKAGE_DESCRIPTION_FILE "${CPACK_RESOURCE_FILE_LICENSE}")
 set(CPACK_PACKAGE_NAME "${CMAKE_PROJECT_NAME}")
 set(CPACK_PACKAGE_VERSION "${CMake_VERSION}")
 set(CPACK_PACKAGE_INSTALL_DIRECTORY "${CPACK_PACKAGE_NAME}")

CMakeLists.txt

@@ -534,7 +534,9 @@ endif()
 
 if(NOT CMake_TEST_EXTERNAL_CMAKE)
   # Install license file as it requires.
-  install(FILES Copyright.txt DESTINATION ${CMAKE_DOC_DIR})
+  install(FILES
+    "${CMake_LICENSE_FILE}"
+    DESTINATION ${CMAKE_DOC_DIR})
 
   # Install script directories.
   install(