Makefile: Remove code to smooth transition to config.status

When commit bdf523e6 made configure generate config.status, it
added a fallback to Makefile to smooth the transition, with a TODO
"code can be removed after QEMU 1.7."  It's been more than five years.
Remove it.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190528082308.22032-2-armbru@redhat.com>

Makefile

@@ -73,14 +73,7 @@ CONFIG_ALL=y
 
 config-host.mak: $(SRC_PATH)/configure $(SRC_PATH)/pc-bios $(SRC_PATH)/VERSION
 	@echo $@ is out-of-date, running configure
-	@# TODO: The next lines include code which supports a smooth
-	@# transition from old configurations without config.status.
-	@# This code can be removed after QEMU 1.7.
-	@if test -x config.status; then \
-	    ./config.status; \
-        else \
-	    sed -n "/.*Configured with/s/[^:]*: //p" $@ | sh; \
-	fi
+	@./config.status
 else
 config-host.mak:
 ifneq ($(filter-out $(UNCHECKED_GOALS),$(MAKECMDGOALS)),$(if $(MAKECMDGOALS),,fail))