ignore .dir-locals.el in cmake build

el/CMakeLists.txt

@@ -4,6 +4,8 @@ mark_as_advanced(SC_EL_BYTECOMPILE)
 file(GLOB scel_sources
      RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} *.el)
 
+list(REMOVE_ITEM scel_sources ".dir-locals.el")
+
 file(GLOB_RECURSE local-load-path
     LIST_DIRECTORIES true
     "~/.emacs.d/site-lisp/*"
@@ -24,12 +26,18 @@ set(all_scel_sources ${scel_sources} sclang-vars.el)
 
 install (FILES ${scel_sources} ${CMAKE_CURRENT_BINARY_DIR}/sclang-vars.el
             DESTINATION share/emacs/site-lisp/SuperCollider)
+
 if (SC_EL_BYTECOMPILE)
     find_program(EMACS_EXECUTABLE emacs)
-	if(NOT EMACS_EXECUTABLE)
+    if(EMACS_EXECUTABLE-NOTFOUND)
         message(SEND_ERROR "Emacs could not be found.\n (If emacs interface is not required, then set SC_EL=no)")
     endif()
 
+    find_program(W3M_EXECUTABLE w3m)
+    if(W3M_EXECUTABLE-NOTFOUND)
+        message(SEND_ERROR "Install w3m to build the help viewer.")
+    endif()
+
     foreach (el ${all_scel_sources})
         add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${el}c
             COMMAND ${EMACS_EXECUTABLE} -batch