no build means *no* build (and less reports), really

It's hard to tell a successful build from a failed one
if downstream hides the exit code; it's useless to continue
a `for' loop if a pipe shoves that to a subshell; well it seems
that a bashism is worth a thousand quirks with extra fds here.
Minor regexp enhancements are also due.

reports.mk made a bit more resilient/prudent either.

Makefile

@@ -30,9 +30,13 @@ $(DIRECT_TARGETS):
 
 export NUM_TARGETS := $(words $(MAKECMDGOALS))
 
+# for pipefail
+SHELL = /bin/bash
+
 # real targets need real work
 %:
 	@n=1; \
+	set -o pipefail; \
 	say() { echo "$$@" >&2; }; \
 	if [ "$(NUM_TARGETS)" -gt 1 ]; then \
 		n="`echo $(MAKECMDGOALS) \

lib/build.mk

@@ -2,7 +2,8 @@
 ANSI_OK   ?= 1;32
 ANSI_FAIL ?= 1;31
 
-GOTCHA := ^(((\*\* )?(E:|[Ee]rror|[Ww]arning).*)|(.* (Stop|failed)\.))$$
+MAX_ERRORS = 3
+GOTCHA := ^(((\*\* )?(E:|[Ee]rror|[Ww]arning).*)|(.* (conflicts|Depends:) .*)|(.* (Stop|failed)\.))$$
 
 ifndef MKIMAGE_PROFILES
 $(error this makefile is designed to be included in toplevel one)
@@ -51,7 +52,9 @@ build-image: profile/populate
 		tail -200 "$(BUILDLOG)" $(SHORTEN) \
 		| GREP_COLOR="$(ANSI_OK)" GREP_OPTIONS="--color=auto" \
 		  grep '^\*\* image: .*$$' ||:; \
+		RETVAL=0; \
 	else \
+		RETVAL=$$?; \
 		echo -n "$(TIME) failed, see log"; \
 		if [ -z "$(DEBUG)" ]; then \
 			echo ": $(BUILDLOG)" $(SHORTEN); \
@@ -61,9 +64,10 @@ build-image: profile/populate
 		fi; \
 		tail -200 "$(BUILDLOG)" \
 		| GREP_COLOR="$(ANSI_FAIL)" GREP_OPTIONS="--color=auto" \
-		  egrep "$(GOTCHA)"; \
+		  egrep -m "$(MAX_ERRORS)" "$(GOTCHA)"; \
 		df -P $(BUILDDIR) | awk 'END { if ($$4 < $(LOWSPACE)) \
 			{ print "NB: low space on "$$6" ("$$5" used)"}}'; \
 	fi; \
 	if [ -n "$(BELL)" ]; then echo -ne '\a'; fi; \
+	exit $$RETVAL; \
 	} >&2

reports.mk

@@ -24,25 +24,31 @@ reports/prep:
 	@mkdir -p "$(REPORTDIR)"
 
 reports/scripts: reports/prep
-	@grep "^mki.*scripts: Run: " $(BUILDLOG) \
-	| sed -rn "s,^.*($(BUILDDIR)|$(SYMLINK))/(.*)'$$,\2,p" \
-	> "$(REPORTDIR)/$*.log" \
-	&& echo "** scripts report: $(REPORTDIR)/$(@F).log" $(SHORTEN)
+	@OUT="$(REPORTDIR)/$(@F).log"; \
+	grep "^mki.*scripts: Run: " $(BUILDLOG) \
+	| sed -rn "s,^.*($(BUILDDIR)|$(SYMLINK))/(.*)'$$,\2,p" > "$$OUT" \
+	&& if [ -s "$$OUT" ]; then \
+		echo "** scripts report: $$OUT" $(SHORTEN); \
+	fi
 
 reports/targets: reports/prep
 	@if ! [ -n "$(REPORT_PATH)" -a -s "$(REPORT_PATH)" ]; then \
 		exit 0; \
 	fi; \
 	if type -t dot >&/dev/null; then \
-		REPORT_IMAGE="$(REPORTDIR)/$(@F).png"; \
+		OUT="$(REPORTDIR)/$(@F).png"; \
 		report-targets < "$(REPORT_PATH)" \
-		| dot -Tpng -o "$$REPORT_IMAGE" \
-		&& echo "** target graph report: $$REPORT_IMAGE"; \
+		| dot -Tpng -o "$$OUT" \
+		&& if [ -s "$$OUT" ]; then \
+			echo "** target graph report: $$OUT"; \
+		fi; \
 	else \
-		REPORT_DOT="$(BUILDDIR)/targets.dot"; \
-		report-targets < "$(REPORT_PATH)" > "$$REPORT_DOT" \
-		&& echo "** graphviz missing, " \
-			"target graph dot file: $$REPORT_DOT"; \
+		OUT="$(BUILDDIR)/targets.dot"; \
+		report-targets < "$(REPORT_PATH)" > "$$OUT" \
+		&& if [ -s "$$OUT" ]; then \
+			echo "** graphviz missing, " \
+				"target graph dot file: $$OUT"; \
+		fi; \
 	fi $(SHORTEN); \
 	mv "$(REPORT_PATH)" "$(REPORTDIR)/$(@F).log"