boost: detect missing selects

boost: detect missing selects

As suggested by Arnout during the review of
http://patchwork.ozlabs.org/patch/934589, add a mechanism to detect a
missing boost select by checking that we do not install a boost library
which hasn't been selected by the user.

To manage a change of boost configuration by the user between two
builds, add a BOOST_PRE_INSTALL_TARGET_HOOKS to remove all boost
libraries before installing them.

Also, use ls with a wildcard instead of test to avoid trying to guess
library names if boost layout is set to tagged or versionned (the
wildcard will also help us to manage shared or static library)

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>