sys-utils/setarch.c: fix build with uclibc-ng < 1.0.39

sys-utils/setarch.c: fix build with uclibc-ng < 1.0.39

Fix the following build failure with uclibc-ng < 1.0.39 (i.e., without
https://github.com/wbx-github/uclibc-ng/commit/85ac4f04d94e98389a8315e720630d0f95bfdfd6)
raised since version 2.39 and
https://github.com/util-linux/util-linux/commit/03a254f010b08da1175f50a8ae7882e59228f1b4:

sys-utils/setarch.c:106:7: error: 'PER_LINUX32_3GB' undeclared here (not in a function); did you mean 'PER_LINUX32'?
  106 |     X(PER_LINUX32_3GB) \
      |       ^~~~~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/fb1feb47f2660882fa53f66bacc63e191fd52175

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>