Since we're updating the tune file format, it makes sense to abstract
the compiler tune arguments at this point too. This means that should
these need to be overridden at any point, the original values can
still be obtained in a similar manner to the other TUNE* variables.

Whilst this isn't strictly necessary for any current need, its likely
good practise to standardise this behaviour.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

There is currently consideradble confusion over how the tune files operate
and how these interact with the rest of the build system. This update/overhaul
changes things so the tune files are primarily resonsible for setting:

TUNE_ARCH - What was formerly set as TARGET_ARCH and is the value that
represents the architecture we're targetting.

TUNE_PKGARCH - The value that represents the tune confuration that this set
of tune parameters results in.

This allows the significant improvement that the core can now always determine
the target architecture value, even when TARGET_ARCH needs to be reset to
something different and likewise, there is one package architecture variable
the core can reference allowing simplification of the BASE_PACKAGE_ARCH, PACKAGE_ARCH
and FEED_ARCH variables.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

This gets us closer to making including tune-<arch>.inc "just work".
Moving the TARGET_ARCH definitions is something for a follup patch.

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

git-svn-id: https://svn.o-hand.com/repos/poky/trunk@2388 311d38ba-8fff-0310-9ca6-ca027cbcb966