avoid setting GLOBAL_* altogether

Applying set() and only set() to a GLOBAL_* is safe
but still a potentially confusing example; so let's
just do it right (and warn unsuspecting folks too).

features.in/bootloader/config.mk

@@ -3,7 +3,7 @@
 # - remember .base if adding yet another *_PACKAGES
 
 use/bootloader: use/install2 sub/main
-	@$(call add,BASE_PACKAGES,alterator-$$(GLOBAL_BASE_BOOTLOADER))
+	@$(call add,BASE_PACKAGES,alterator-$$(BASE_BOOTLOADER))
 
 use/bootloader/grub use/bootloader/lilo: use/bootloader/%: use/bootloader
-	@$(call set,GLOBAL_BASE_BOOTLOADER,$*)
+	@$(call set,BASE_BOOTLOADER,$*)

features.in/install2/install2/stage2cfg.mk

@@ -8,6 +8,9 @@ MKI_PACK_RESULTS = squash:altinst
 # also removed in a cleanup hook but to spare a few cycles...
 HSH_EXCLUDE_DOCS = 1
 
+# pass downstream
+GLOBAL_BASE_BOOTLOADER := $(BASE_BOOTLOADER)
+
 debug:
 	@echo "** install2: IMAGE_PACKAGES: $(IMAGE_PACKAGES)"
 	@echo "** install2: IMAGE_PACKAGES_REGEXP: $(IMAGE_PACKAGES_REGEXP)"

functions.mk

@@ -15,6 +15,7 @@ endef
 # add() just appends an additive rule...
 add = $(and $(1),$(2),$(add_body))
 define add_body
+$(if $(filter GLOBAL_% INFO_%,$(1)),$(warning add,$(1) might be a problem)) \
 { $(log_body); \
 printf '%s += %s\n' '$(1)' '$(2)' >> "$(CONFIG)"; }
 endef