Preliminary changes for PowerPC 64-bits support

These changes allow to build SlapOS on Debian Buster ppc64el.

The PowerPC 64-bits little endian platform appeared more recently into autoconf and therefore needed updated `config.sub` and `config.guess` files.

Somehow these only needed to be patched on autoconf itself which is quite dated (2012), and libyaml that does not ship it's own `config.sub` and `config.guess` files. Other components built fine out of the box.

`config.sub` and `config.guess` files were taken from Debian Buster itself. More information at: https://wiki.debian.org/AutoTools/autoconf

**This merge request would have to be backported to previous releases in the case components reference older releases of SlapOS, which, if I understand correctly, is the case some times.**

See merge request nexedi/slapos!780

component/autoconf/buildout.cfg

@@ -3,6 +3,7 @@ extends =
   ../m4/buildout.cfg
   ../patch/buildout.cfg
   ../perl/buildout.cfg
+  ../gnu-config/buildout.cfg
 parts =
   autoconf
 
@@ -11,6 +12,7 @@ recipe = slapos.recipe.cmmi
 shared = true
 url = http://ftp.gnu.org/gnu/autoconf/autoconf-2.69.tar.gz
 md5sum = 82d05e03b93e45f5a39b828dc9c6c29b
+pre-configure = cp -f ${gnu-config:location}/config.sub ${gnu-config:location}/config.guess build-aux/
 patch-options = -p1
 patches =
   ${:_profile_base_location_}/autoconf-2.69-shebang_workaround.patch#9d286e6f9c271dff361891e381be706d

component/gnu-config/buildout.cfg

+[gnu-config]
+recipe = slapos.recipe.cmmi
+shared = true
+url = https://git.savannah.gnu.org/gitweb/?p=config.git;a=snapshot;h=5e531d391852a54e7fab2d8ff55625fca514b305;sf=tgz
+md5sum = ffe323c69b6f21aa28e900f76febd3d6
+configure-command = :
+make-targets =  
+make-binary = cp -r . @@LOCATION@@
\ No newline at end of file

component/libyaml/buildout.cfg

 [buildout]
+extends = ../gnu-config/buildout.cfg
 
 parts =
   libyaml
@@ -8,3 +9,4 @@ recipe = slapos.recipe.cmmi
 shared = true
 url = http://pyyaml.org/download/libyaml/yaml-0.1.6.tar.gz
 md5sum = 5fe00cda18ca5daeb43762b80c38e06e
+pre-configure = cp -f ${gnu-config:location}/config.sub ${gnu-config:location}/config.guess config/
\ No newline at end of file