Don't ignore failure when doing 'make ci'

The best way to use 'make ci' is 'make -k ci', then it
will complete its run even if a version fails, and still
exit with an error code.

circle.yml

@@ -12,5 +12,5 @@ dependencies:
 
 test:
   override:
-    - make ci:
+    - make -k ci:
         timeout: 3600

erlang.mk

@@ -5376,7 +5376,7 @@ ci_verbose = $(ci_verbose_$(V))
 
 define ci_target
 ci-$(1): $(CI_INSTALL_DIR)/$(1)
-	-$(ci_verbose) \
+	$(ci_verbose) \
 		PATH="$(CI_INSTALL_DIR)/$(1)/bin:$(PATH)" \
 		CI_OTP_RELEASE="$(1)" \
 		CT_OPTS="-label $(1)" \