UPSTREAM: Makefile: Just error out if no .config exists

Currently coreboot runs the 'config' command if no .config file exists.
This isn't what anyone wants, and is particularly frustrating for tools
that automate the build, where the build just hangs waiting for input.

Instead, just show an error message and then exit the build.

BUG=none
BRANCH=none
TEST=none

Change-Id: I8770f1f9be6990ca190a9fea78f340e0574e46bd
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 20aa043b44
Original-Change-Id: If9e0c2c26f8273814518589a2f94c5b00fc4cefe
Original-Signed-off-by: Martin Roth <martinroth@google.com>
Original-Reviewed-on: https://review.coreboot.org/18245
Original-Tested-by: build bot (Jenkins)
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://chromium-review.googlesource.com/433982

Makefile

@@ -123,8 +123,11 @@ endif
 ifeq ($(NOCOMPILE),1)
 include $(TOPLEVEL)/Makefile.inc
 include $(TOPLEVEL)/payloads/Makefile.inc
-real-all: config
-
+real-all:
+	@echo "Error: Expected config file ($(DOTCONFIG)) not present." >&2
+	@echo "Please specify a config file or run 'make menuconfig' to" >&2
+	@echo "generate a new config file." >&2
+	@exit 1
 else
 
 include $(DOTCONFIG)