Changes

dist: fix embedders autogen by adding standalone-directories to
embedded tarball
Embedders don't get utils,tests,contrib/*,doc,... directories in their 
tarball because they build hwloc in embedded mode. However it means
their tarballs cannot be re-autogen'ed because automake fails when
those directories are missing
(automake doesn't know if we're in embedded or standalone mode).
OMPI didn't have any issue in the past because they manually copied 
hwloc embedded directories AND created standalone subdirectories that 
their automake would dist. Now that they use hwloc as git submodule,
bring the proper fix inside hwloc so that OMPI doesn't have to hardwire
that list of subdirectories anymore.
Refs open-mpi/ompi#7363
Note that pure-hwloc embedded tarballs still cannot be re-autogen'ed 
because they needs many more standalone files
(e.g. all .in files used by configure) but we do not care.
Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
(cherry picked from commit b332c934dc134bbfd2121d6fc6c22234c32cec19)

tests/embedded: check that embedders can autogen using the hwloc
embedded tarball
Build an embedded tarball from the original tarball and use it instead 
for all tests.
The intend is to have our CI detect problems such as open-mpi/ompi#7363 
whenever the list of non-embedded dist directories changes.
Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
(cherry picked from commit 88fc5b4e37b980c56deb6a55c6acb393349ff8b9)