rework isoboot support beyond x86

Every .iso was assumed to be bootable since the very beginning[*],
and isoboot images were deemed to be x86 isolinux ones; this didn't
change with basic ppc/armh support as I never ran into hardware
that would _boot_ those ISOs, not only run the code, and it was
only e2k isodata project that finally forced this refactoring.

It's still not perfect: pack and syslinux features still end up
somewhat interwoven, and too much places care for architecture
the image is being built for (instead of archdep features tossing
their appropriate bits and pieces in).

Should help:
- any-arch regarding isodata images;
- {x86,aarch64}/efi by decoupling isoboot and isolinux;
- ppc{,64} as introducing yaboot support will be easier now;
- mipsel{,64} too, hopefully.

* I knew of school addon images baked with mkimage-profiles-desktop
  but postponed and then neglected the whole problem for years...

conf.d/test.mk

@@ -3,7 +3,7 @@ ifneq (,$(DEBUG))
 
 ifeq (distro,$(IMAGE_CLASS))
 
-distro/syslinux-auto: distro/.init use/hdt use/syslinux/timeout/1; @:
+distro/syslinux-auto: distro/.boot use/hdt use/syslinux/timeout/1; @:
 distro/syslinux-noescape: distro/syslinux-auto use/syslinux/noescape.cfg; @:
 
 distro/live-systemd: distro/.base use/live/base +systemd; @:

features.in/build-distro/lib/90-build-distro.mk

@@ -11,12 +11,16 @@ BOOT_BIBL := $(META_BIBLIO)
 BOOT_ABST := $(META_ABSTRACT)
 DATE_F    := $(shell date +%F)
 
-### we might want a e2k data iso too
+ifeq (isodata,$(IMAGE_PACKTYPE))
+BOOT_TYPE :=
+else
 ifeq (,$(filter-out e2k%,$(ARCH)))
 BOOT_TYPE := e2kboot
-else
+endif
+ifeq (,$(filter-out i586 x86_64,$(ARCH)))
 BOOT_TYPE := isolinux
 endif
+endif
 
 all: | $(GLOBAL_DEBUG) prep copy-subdirs copy-tree run-scripts pack-image \
 	postprocess $(GLOBAL_CLEAN_WORKDIR)

features.in/pack/config.mk

@@ -6,14 +6,9 @@ DISTRO_EXTS := .iso
 use/pack:
 	@$(call add_feature)
 
-# conventional ISO9660 image hybridization
+# fallback type is isodata, might get set elsewhere to produce bootable iso
-# for direct bootable usbflash imaging
+use/pack/iso: use/pack
-use/pack/iso: use/pack boot/isolinux $(ISOHYBRID:%=use/isohybrid)
+	@$(call try,IMAGE_PACKTYPE,isodata)
-ifeq (distro,$(IMAGE_CLASS))
-	@$(call set,IMAGE_PACKTYPE,boot)
-else
-	@$(call set,IMAGE_PACKTYPE,isodata)
-endif
 
 # virtual environments
 VE_ARCHIVES := tar cpio ubifs

features.in/syslinux/config.mk

@@ -1,10 +1,12 @@
 # default is plain text prompt
-use/syslinux: sub/stage1
+# NB: might be usbflash-ready hybrid iso
+use/syslinux: sub/stage1 $(ISOHYBRID:%=use/isohybrid)
 	@$(call add_feature)
 	@$(call add,STAGE1_PACKAGES,syslinux)
 	@$(call try,META_SYSTEM_ID,SYSLINUX)
 	@$(call try,BOOTVGA,normal)
 	@$(call set,RELNAME,ALT ($(IMAGE_NAME)))
+	@$(call set,IMAGE_PACKTYPE,boot)
 
 # UI is overwritten
 use/syslinux/ui/%: use/syslinux

features.in/syslinux/lib/90-syslinux.mk

@@ -0,0 +1 @@
+BOOT_TYPE := isolinux

lib/boot.mk

@@ -3,13 +3,17 @@ $(error this makefile is designed to be included in toplevel one)
 endif
 
 ifeq (distro,$(IMAGE_CLASS))
+
+# install x86 media bootloader
 ifeq (,$(filter-out i586 x86_64,$(ARCH)))
-# install media bootloader
+boot/iso: use/syslinux
-boot/isolinux: use/syslinux
 	@$(call set,BOOTLOADER,isolinux)
 endif
+
+# firmware is the bootloader
 ifeq (,$(filter-out e2k%,$(ARCH)))
-boot/isolinux:
+boot/iso:
 	@$(call set,BOOTLOADER,e2k-boot)
 endif
+
 endif

lib/distro.mk

@@ -12,13 +12,15 @@ distro/.init: profile/bare
 	@$(call try,META_APP_ID,$(IMAGE_NAME))
 	@$(call set,META_PUBLISHER,ALT Linux Team)
 
-# NB: the last flavour in KFLAVOURS gets to be the default one;
+distro/.boot: distro/.init boot/iso
-# the kernel packages regexp evaluation has to take place at build stage
-distro/.base: distro/.init use/kernel
-	@$(call set,META_SYSTEM_ID,LINUX)
 	@$(call set,META_VOL_ID,ALT $(IMAGE_NAME)/$(ARCH))
 	@$(call set,META_VOL_SET,ALT)
 
+# NB: the last flavour in KFLAVOURS gets to be the default one;
+# the kernel packages regexp evaluation has to take place at build stage
+distro/.base: distro/.boot use/kernel
+	@$(call set,META_SYSTEM_ID,LINUX)
+
 # this one should not be fundamental as it appears (think armh)
 distro/.installer: distro/.base use/bootloader/grub +installer; @: