execute_process(COMMAND ${SIZE_TOOL} ${ELF} OUTPUT_VARIABLE _out RESULT_VARIABLE _res)
if(NOT _res EQUAL 0)
	message(FATAL_ERROR "avr-size failed")
endif()
# avr-size line 2 is "<text> <data> <bss> <dec> <hex> <file>".
string(REGEX MATCH "\n[ \t]*([0-9]+)" _m "${_out}")
set(_text ${CMAKE_MATCH_1})
if(_text GREATER LIMIT)
	message(FATAL_ERROR ".text is ${_text} bytes, over the ${LIMIT}-byte boot section")
endif()
message(STATUS ".text ${_text} <= ${LIMIT} (boot section budget)")