CMAKE_MESSAGE_INDENT

The message() command joins the strings from this list and for log levels of NOTICE and below, it prepends the resultant string to each line of the message.

Example:

list(APPEND listVar one two three)

message(VERBOSE [[Collected items in the "listVar":]])
list(APPEND CMAKE_MESSAGE_INDENT "  ")

foreach(item IN LISTS listVar)
  message(VERBOSE ${item})
endforeach()

list(POP_BACK CMAKE_MESSAGE_INDENT)
message(VERBOSE "No more indent")

Which results in the following output:

-- Collected items in the "listVar":
--   one
--   two
--   three
-- No more indent