Merge "Error out if MALLOC_IMPL is defined."

ifeq ($(TARGET_ARCH),)

  $(error TARGET_ARCH not defined by board config: $(board_config_mk))

endif

ifneq ($(MALLOC_IMPL),)

  $(warning *** Unsupported option MALLOC_IMPL defined by board config: $(board_config_mk).)

  $(error Use `MALLOC_SVELTE := true` to configure jemalloc for low-memory)

endif

TARGET_DEVICE_DIR := $(patsubst %/,%,$(dir $(board_config_mk)))

board_config_mk :=