[CMake] Always create rootcint and genreflex as copies of rootcling

Always create `rootcing` and `genreflex` as copies of rootcling to make
the install code more robust.

Right now, we use some `install(CODE "execute_process(COMMAND ln -f ...`
solution on unix to install `rootcint` and `genreflex`. This does not
work in all cases, either because of the usage of `\$ENV{DESTDIR}` when
`DESTDIR` is not set, or because hard links are not allowed.

Always copying `rootcling` - already in the build tree - makes things
simpler and more robust, at very little cost (`rootcling` is only 31K,
so copying two times only increases the size of ROOTs `bin` directory by
1.5 %).

Author: guitargeek

main/CMakeLists.txt

@@ -114,32 +114,26 @@ endif()
 ROOT_EXECUTABLE(rootls src/rootls.cxx LIBRARIES RIO Tree Core Rint ROOTNTuple)
 
 # Create aliases: rootcint, genreflex.
-if(WIN32)
-  add_custom_command(TARGET rootcling POST_BUILD
-                     COMMAND copy /y rootcling.exe rootcint.exe
-                     COMMAND copy /y rootcling.exe genreflex.exe
-                     WORKING_DIRECTORY ${CMAKE_RUNTIME_OUTPUT_DIRECTORY})
-else()
-  add_custom_command(TARGET rootcling POST_BUILD
-                     COMMAND ln -f rootcling rootcint
-                     COMMAND ln -f rootcling genreflex
-                     WORKING_DIRECTORY ${CMAKE_RUNTIME_OUTPUT_DIRECTORY})
-endif()
-set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES
-                         "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/rootcint;${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/genreflex")
+add_custom_command(
+  TARGET rootcling POST_BUILD
+  COMMAND ${CMAKE_COMMAND} -E copy_if_different $<TARGET_FILE:rootcling> ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/rootcint
+  COMMAND ${CMAKE_COMMAND} -E copy_if_different $<TARGET_FILE:rootcling> ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/genreflex
+  COMMENT "Creating copies rootcint and genreflex of rootcling"
+)
 
-if(CMAKE_HOST_UNIX)
-  install(CODE "execute_process(COMMAND ln -f rootcling rootcint WORKING_DIRECTORY \$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR})" COMPONENT applications)
-  install(CODE "execute_process(COMMAND ln -f rootcling genreflex WORKING_DIRECTORY \$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR})" COMPONENT applications)
-else()
-  if(MSVC)
-    install(PROGRAMS  ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/rootcling.exe DESTINATION ${CMAKE_INSTALL_BINDIR} COMPONENT applications)
-    install(PROGRAMS  ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/rootcint.exe DESTINATION ${CMAKE_INSTALL_BINDIR} COMPONENT applications)
-    install(PROGRAMS  ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/genreflex.exe DESTINATION ${CMAKE_INSTALL_BINDIR} COMPONENT applications)
-  else()
-    install(PROGRAMS  ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/rootcint
-                      ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/genreflex
-                      ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/rlibmap
-                      DESTINATION ${CMAKE_INSTALL_BINDIR} COMPONENT applications)
-  endif()
-endif()
+# Ensure aliases are cleaned up by `make clean`.
+set_property(
+  DIRECTORY
+  APPEND
+  PROPERTY ADDITIONAL_MAKE_CLEAN_FILES
+    "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/rootcint"
+    "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/genreflex"
+)
+
+# Install the aliases
+install(PROGRAMS
+  ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/rootcint
+  ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/genreflex
+  DESTINATION ${CMAKE_INSTALL_BINDIR}
+  COMPONENT applications
+)