Now that overrides get expanded 'on the fly', change appendVar
and prependVar to work using _append and _prepend, else we'd have
to re-implement pieces of getVar and the timing of expansions
becomes problematic.
Using _append/_prepend equivalence gives the behaviour users likley
expect from these functions.
(Bitbake rev: 40d661aaf7a563c6447b073310c5f2fdae6ca3d0)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
4c386e1dd5