Instead of reusing a "target_section" variable, name them host and build
section instead. This patch sets things up for other improvementsm,
separating out the renaming.
(From OE-Core rev: 279b809e8306b0eb6ae6caeb6b0a3c3c62d2f9d2)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>