Previously cross-compilation would fail:
CC xvasprintf.o
xstrtol-error.c:50:16: warning: 'struct rpl_option' declared inside parameter list
int exit_status)
^
xstrtol-error.c: In function 'xstrtol_error':
xstrtol-error.c:84:5: error: invalid use of undefined type 'struct rpl_option'
* gnu/packages/patches/diffutils-getopt.patch: New file.
* gnu/packages/base.scm (diffutils)[source]: Use it.
* gnu/local.mk (dist_patch_DATA): Add it.