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
-  DOC "The pandoc software, to build the man page from the rst documentation")
-if(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})
+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)
+    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