arch/powerpc: add powerpc64le support

Technically, I don't forbid powerpcle support either, but I'm not sure that
there is any library/compiler support for that at the moment (though the hw
technically makes it possible).

powerpc64le needs glibc 2.19 and gcc 4.9. I haven't looked into the support
tools, but at least gdb 7.5 is too old (7.7.1 definitely has support).

Also make powerpc64 non-experimental. It's practically old at this point.

Signed-off-by: Cody P Schafer <dev@codyps.com>
[yann.morin.1998@free.fr: use ${target_endian_le} and ${target_bits_64}]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <64bfbbced9dd8f62e0d6.1399801945@gun>
Patchwork-Id: 347775

 do not bother running ldconfig on DESTDIR.  it wants to write the temp cache

 file outside of the chroot.  doesnt matter anyways as we wont use the cache

 results (portage will rebuild cache), so running ldconfig is simply a waste

 of time.

 diff -durN glibc-2.13.orig/Makefile glibc-2.13/Makefile

 --- glibc-2.13.orig/Makefile	2009-04-23 20:23:03.000000000 +0200

 +++ glibc-2.13/Makefile	2009-11-13 00:49:49.000000000 +0100

 @@ -116,6 +116,7 @@

  	rm -f $(symbolic-link-list)

  install:

 +dont-bother-with-destdir:

  	-test ! -x $(common-objpfx)elf/ldconfig || LC_ALL=C LANGUAGE=C \

  	  $(common-objpfx)elf/ldconfig $(addprefix -r ,$(install_root)) \

  				       $(slibdir) $(libdir)