The extension can be different for every link variant.
This change was submitted by Pavel Pisa and Pavel Nemecek.
# Used to load program to the target hardware
define LOAD_PROGRAM_template
.PHONY: load-$(1)$(3:%=-%)
-load-$(1)$(3:%=-%): $(2)/$(1)$(3:%=-%)$(LOAD_EXTENSION)
+load-$(1)$(3:%=-%): $(2)/$(1)$(3:%=-%)$(if $(LOAD_EXTENSION-$(3)),$(LOAD_EXTENSION-$(3)),$(LOAD_EXTENSION))
@$(QUIET_CMD_ECHO) " LOAD $$<"
@if [ -z '$$(LOAD_CMD$(3:%=-%))' ]; then echo "No command for loading applications to '$(3)' is specified."; exit 1; fi
$(Q) $$(LOAD_CMD$(3:%=-%)) $$<