manibuilder: Let build tests fail with the original error code

We can still run all tests with `make -k`.

Change-Id: Ib59b8863186e5f7ecbaa2aa65cdbd51913dcf8e7
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/70913
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/util/manibuilder/Makefile b/util/manibuilder/Makefile
index aff150f..294bc28 100644
--- a/util/manibuilder/Makefile
+++ b/util/manibuilder/Makefile
@@ -67,7 +67,8 @@
 		 $(if $(STRIP),STRIP='$(STRIP)') \
 		 $(if $(LIBS_BASE),LIBS_BASE='$(LIBS_BASE)') \
 		 $(MAKEARGS)" \
-		$(if $(QUIET_TEST),>/dev/null 2>&1) || echo $*: $$?
+		$(if $(QUIET_TEST),>/dev/null 2>&1) \
+			|| { RET=$$?; echo $*: $${RET}; exit $${RET}; }
 
 $(addsuffix -shell,$(ALL_TAGS)): %-shell: %-check-build
 	$(QUIET_SETUP)\