building -8 tools under -10 fails (redefinition of be32enc)

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

Trying to build -8 under -10 fails during the tools build:

#   compile  libctf/ctf_create.lo
cc -O  -DCTF_OLD_VERSIONS -I/usr/src-8/tools/libctf/../compat  -I/usr/src-8/tools/libctf/../../external/cddl/osnet/sys  -I/usr/src-8/tools/libctf/../../external/cddl/osnet/include  -I/usr/src-8/tools/libctf/../../external/cddl/osnet/dist/head  -I/usr/src-8/tools/libctf/../../external/cddl/osnet/dist/common/ctf  -I/usr/src-8/tools/libctf/../../external/cddl/osnet/dist/lib/libctf/common  -I/usr/src-8/tools/libctf/../../external/cddl/osnet/dist/uts/common  -I/usr/src-8/tools/libctf/../../external/bsd/elftoolchain/dist/libelf -DHAVE_NBTOOL_CONFIG_H=1 -D_FILE_OFFSET_BITS=64  -I/var/work/obj-8/tooldir.NetBSD-10.1-amd64/include/compat -I/usr/src-8/tools/compat  -DHAVE_NBTOOL_CONFIG_H=1 -D_FILE_OFFSET_BITS=64 -I/var/work/obj-8/tooldir.NetBSD-10.1-amd64/include -I/var/work/obj-8/tooldir.NetBSD-10.1-amd64/include/nbinclude -c -o ctf_create.lo.o    /usr/src-8/tools/libctf/../../external/cddl/osnet/dist/common/ctf/ctf_create.c
In file included from /var/work/obj-8/tooldir.NetBSD-10.1-amd64/include/compat/nbtool_config.h:871,
                 from /usr/src-8/tools/libctf/../../external/cddl/osnet/dist/common/ctf/ctf_create.c:23:
/usr/src-8/tools/libctf/../compat/compat_defs.h:1091:22: error: redefinition of 'be16enc'
 1091 | __GEN_ENDIAN_ENC(16, be)
      |                      ^~
/usr/src-8/tools/libctf/../compat/compat_defs.h:1085:1: note: in definition of macro '__GEN_ENDIAN_ENC'
 1085 | endian ## bits ## enc(void *dst, uint ## bits ## _t u) \
      | ^~~~~~
In file included from /usr/include/amd64/endian.h:3,
                 from /usr/src-8/tools/libctf/../../external/cddl/osnet/sys/machine/endian.h:32,
                 from /usr/include/sys/types.h:98,
                 from /usr/src-8/tools/libctf/../../external/cddl/osnet/sys/sys/types.h:77,
                 from /usr/src-8/tools/libctf/../compat/compat_defs.h:35,
                 from /var/work/obj-8/tooldir.NetBSD-10.1-amd64/include/compat/nbtool_config.h:871,
                 from /usr/src-8/tools/libctf/../../external/cddl/osnet/dist/common/ctf/ctf_create.c:23:
/usr/include/sys/endian.h:207:1: note: previous definition of 'be16enc' was here
  207 | __GEN_ENDIAN_ENC(16, be)
      | ^~~~~~~~~~~~~~~~