libatlas: use uname -m to detect arch.

output of uname -p is "unknown" for soem processors, leading to use 32bits on 64bits machine.

component/libatlas/buildout.cfg

@@ -30,7 +30,7 @@ configure-options =
   --prefix=${buildout:parts-directory}/${:_buildout_section_name_}
   --with-netlib-lapack-tarfile=${lapack-download:location}/${lapack-download:filename}
   --shared
-  -b "$(uname -p | grep -q 64 && echo 64 || echo 32)"
+  -b "$(uname -m | grep -q 64 && echo 64 || echo 32)"
   -Fa alg '-fPIC'
 make-options =
   -C build