See: https://bugzilla.altlinux.org/48863

check conditions of  make  for equality of variables with an empty value
instead of check definition.
A defined but empty variable under all these conditions results errors.

build.log does not exist when they run, because the build directory
is no longer created to run them.

This one extracts the exact time-ordered list of script hooks
run while building the image.

Some commons refactoring is also due.

There is at least one known deficiency for mkimage-profiles:
build.log will be truncated if verbose mode is enabled and
hasher version is lower than 1.3.22.

The check is done here since it's where the logging is arranged,
and doing it in image.in/Makefile would result in the warning
about log-truncating software being truncated by the said software.

Thanks Max Kosmach for reporting this inobviousity.

The former toplevel Makefile is now toplevel main.mk;
this change allows for multi-target, multi-arch processing
in the current toplevel Makefile.

As the "build" symlink semantics change quite considerably
when one is doing bulk builds (several pruned builddirs might
be useful for comparison), BUILDDIR is now much more likely
to be recreated: the cases when it will persist are when it's
either a single-image build or when the prefix hasn't changed.

There are some more or less subtle bugfixes and enhancements
all over the map as well.

Done within 20111230..20120102 timeframe, actually...

Preferences might be somewhat interesting too: while the official
ones shouldn't influence the build result at all, there's no whitelist
so all kinds of weirdness can be stuffed into local config in principle.
That should be diagnosable at least.

Thanks torabora@ for yet again seemingly obvious feature request
which strangely managed to evade implementation before.

On an afterthought, mass builds would suggest too much coffee
instead of a progress indicator -- so implemented the latter.

NB: the actual downstream-make-calling rule would expand the "naive"
$(shell date) too early: the rule is evaluated before starting its
execution, and as it's the time consuming one the shell evaluation
was in need, not make's.  The result is less generally available
(needs to be double quoted and won't work inside e.g. awk programs)
but way more precise.

This is quite a large-scale change since mkimage-profiles got used to
baking distributions over the last year, and virtual environments are
quite different, so e.g. image.in/Makefile had to be split in two with
the main part of it moved into features.in/iso/lib/.

Short overview:

- features.in/Makefile: lib/ support
  (supporting VE images requires dynamic modifications
  to image.in/Makefile before starting the build;
  the most natural way to achieve that seems to use
  features mechanism along with makefile include dir)

- packaging format related part moved into features.in/pack
  (should be better prepared for diversity either)
- features.in/iso renamed to features.in/build-distro
- features.in/ve  renamed to features.in/build-ve
  + NB: these could not be merged as e.g. features.in/build
    due to completely different script hooks

- lib/image.mk renamed to lib/build.mk
- image, config, log postprocessing moved downstream
- added a sort of a topping in the form of lib/sugar.mk
- assorted style fixups (like ifeq usage)

- clean.mk: reliability fix (the problem was observed by Oleg Ivanov
  and me too but finally it did get the attention quantum)

- reviewed, updated and extended docs
  + QUICKSTART: should be[come] a step-by-step guide
    (thanks Leo-sp50 for prodiving feedback)

make CLEAN=1 will prune workdirs after packing their results,
so disk (or preferably tmpfs) usage will be lower

In particular:
- .base is now generated from pieces (see image.in/Makefile)
- s/DISTROS/IMAGES/g; s/CONFIGS/DISTROS/g (for clarity)
- s/DISK_LISTS/MAIN_LISTS/g ("disk" was early m-p-d legacy)
- introduced BASE_PACKAGES to complement BASE_LISTS
- minor tweaks to Makefile (ARCH and DATE moved elsewhere)
- libdistro.mk: dropped overlooked IMAGE_INIT_LIST copy
- clean.mk: silly cleanup

...and some more cosmetic fixes

- image.in/functions.mk: rework kpackage()
  + it takes two arguments explicitly now: this adds some noise
    for "generic" invocations but is rather less messy with recently
    introduced STAGE1_KFLAVOUR (which in its turn is rather cleaner
    than messing with KFLAVOURS, especially since soemthing changed
    in presumably apt and we can't rely on kernel packages being
    installed in the order formed).
- BUILDDIR/DEBUG related fixes
  + Makefile: BUILDDIR initialization moved to distro.mk
- build.log += git info

Now we don't dump all the gory details onto thee
but rather log them handsomely and present only
the most important details by default; use DEBUG=1
and/or BUILDLOG=/path/to/file to tweak.

Also introduced IMAGEDIR and IMAGENAME.

The rest:
- ovz-smp is no more
- base-l10n pkglist (suggested by Alexander Kuprin)
- clean.mk:
  + fixed an oversight: the test result erroneously applied
    only to the first command of several ones that should be
    run iff build/ is a symlink
  + drop implicit rules (it's no C code)
- Makefile: more reasonable iso names
- image.in/Makefile: .disk/date too