define approx_original_sources :=
${SOURCES}
endef
export approx_original_sources

ifdef approx

BOOTSTRAP := ${approx}
define SOURCES =
deb ${approx} stretch main
endef

else ifdef raspi

BOOTSTRAP := http://localhost/raspbian
define SOURCES =
deb http://localhost/raspbian stretch main non-free firmware rpi
deb http://localhost/rpidebian stretch main
endef

else

BOOTSTRAP := http://localhost/debian
define SOURCES =
deb http://localhost/debian stretch main
endef

endif

.PHONY: _approx_restore_sources
_config: _approx_restore_sources
_approx_restore_sources: ${CFGROOT}
	printf '%s\n' "$${approx_original_sources}" >"$${CFGROOT}/etc/apt/sources.list"