[build] Use variants

- Move helpers functions into build/helpers.mak
- Move official warning into official targets only

ion/Makefile

@@ -15,8 +15,6 @@ include ion/src/$(PLATFORM)/Makefile
 -include ion/test/$(PLATFORM)/Makefile
 include ion/src/shared/tools/Makefile
 
-ion_console_display_src += ion/src/shared/console_display.cpp
-
 # We need to work around a GCC bug (concerning versions < 5.1). It is valid in
 # C++11 to initialize a character array by providing a string litteral (e.g.
 # char test[4]= "ab"; is valid and should initialize test to 'a','b',0,0).
@@ -25,10 +23,13 @@ initializer_list = $(shell echo $(1) | sed  "s/\(.\)/'\1',/g")0
 $(call object_for,ion/src/shared/platform_info.cpp): SFLAGS += -DPATCH_LEVEL="$(call initializer_list,$(PATCH_LEVEL))" -DEPSILON_VERSION="$(call initializer_list,$(EPSILON_VERSION))"
 
 ion_src += $(addprefix ion/src/shared/, \
+  console_display.cpp:+consoledisplay \
   console_line.cpp \
   crc32_eat_byte.cpp \
   decompress.cpp \
   events.cpp \
+  events_keyboard.cpp \
+  events_modifier.cpp \
   platform_info.cpp \
   storage.cpp \
   unicode/utf8_decoder.cpp\
@@ -49,14 +50,3 @@ tests_src += $(addprefix ion/test/,\
 ifdef ION_STORAGE_LOG
 SFLAGS += -DION_STORAGE_LOG=1
 endif
-
-# Configure variants
-ion_all_src = $(ion_src)
-ion_all_src += $(ion_simulator_sdl_src) $(ion_simulator_headless_src)
-ion_all_src += $(ion_device_dfu_relocated_src) $(ion_device_dfu_xip_src)
-ion_all_src += $(ion_console_display_src) $(ion_console_stdio_src) $(ion_console_uart_src)
-
-ion_default_src = $(ion_src) $(ion_simulator_sdl_src) $(ion_device_dfu_relocated_src) $(ion_console_stdio_src)
-ion_console_on_screen_src = $(ion_src) $(ion_simulator_sdl_src) $(ion_device_dfu_relocated_src) $(ion_console_display_src)
-ion_xip_src = $(ion_src) $(ion_simulator_sdl_src) $(ion_device_dfu_xip_src) $(ion_console_uart_src)
-ion_headless_src = $(ion_src) $(ion_simulator_headless_src) $(ion_device_dfu_relocated_src) $(ion_console_stdio_src)