[fix] Clean-up out-of-tree building
Adapted to the new master from a patch sent by @cfoyer When building out of tree as the, make sure that target refer to relative paths. This commit also clean-up the usage of the flags and defines a per-target definition of flags (can be changed for a AM_CPPFLAGS if the global definition is good enough). Signed-off-by: Clement Foyer <cfoyer@cray.com> Also adds Clement to the authors list.