Samples: microblaze(el) linux single lib, preset CFLAGS

Build microblaze(el) linux toolchains without
multi-lib, and the default libs should have CFLAGS set
to match Low End Linux profile in XPS

Signed-off-by: David Holsgrove <david.holsgrove@xilinx.com>
Microblaze has moved into glibc libc proper and is no longer a port

No longer need to request --enable-ports when building glibc,
as microblaze has been moved from the ports subdir into the core libc
for glibc 2.19+

Signed-off-by: David Holsgrove <david.holsgrove@xilinx.com>