Display a message to tell if we found pandoc or not

fix #3177

CMakeLists.txt

@@ -65,15 +65,20 @@ execute_process(COMMAND "date" "+%Y-%m-%d" OUTPUT_VARIABLE DOC_DATE
                 OUTPUT_STRIP_TRAILING_WHITESPACE)
 set(MAN_PAGE ${CMAKE_CURRENT_BINARY_DIR}/doc/${PROJECT_NAME}.1)
 set(DOC_PAGE ${CMAKE_CURRENT_SOURCE_DIR}/doc/${PROJECT_NAME}.1.rst)
-find_program(PANDOC_EXECUTABLE NAMES pandoc
+if (NOT PANDOC_EXECUTABLE)
+  find_program(PANDOC_EXECUTABLE NAMES pandoc
     DOC "The pandoc software, to build the man page from the rst documentation")
-if(PANDOC_EXECUTABLE)
+  if(PANDOC_EXECUTABLE)
+    message(STATUS "Found Pandoc: ${PANDOC_EXECUTABLE}")
     set(WITH_DOC true)
     file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/doc/)
     add_custom_command(OUTPUT ${MAN_PAGE}
       COMMAND ${PANDOC_EXECUTABLE} -M date="${DOC_DATE}" -s -t man ${DOC_PAGE} -o ${MAN_PAGE}
       DEPENDS ${DOC_PAGE})
     add_custom_target(doc ALL DEPENDS ${MAN_PAGE})
+  else()
+    message(STATUS "Pandoc not found, documentation cannot be built")
+  endif()
 endif()
 
 # Look for litesql and enable the database if found