[PATCH 0/4] build: minimize rebuilds

[Sam Ravnborg]

Following patchset minimizes re-builds.
With the setup I use at the moment where I run
build tests on 100+ arm related boards I see that the
build time is reduced to half - for an otherwise
clean build with no changes.
In other words - the wall clock time for a
simple "try to build all boards" where nothing
has changed goes from ~2:35 minutes to 1:21 minutes

The patches has been tested in my local setup - and
no missing rebuilds was seen.

Sam Ravnborg (4):
      build: fix that defaultenv is always rebuilt
      build: fix that passwd.h is always built
      build: fix that the bbenv file is always rebuilt
      build: fix that LZO file is always rebuilt

 common/Makefile        | 28 +++++++++++++++-------------
 defaultenv/Makefile    |  4 ++--
 scripts/Kbuild.include | 12 +++++++-----
 scripts/Makefile.lib   |  2 +-
 4 files changed, 25 insertions(+), 21 deletions(-)