Set TERM within the systemd-nspawn container in makechrootpkg

This is required by WINE to prevent
```
unknown: I need something more specific
```

src/makechrootpkg.in

@@ -382,6 +382,7 @@ download_sources
 prepare_chroot
 
 nspawn_build_args=(
+	--setenv=TERM=xterm
 	--bind="${PWD//:/\\:}:/startdir"
 	--bind="${SRCDEST//:/\\:}:/srcdest"
 	--tmpfs="/tmp:${tmp_opts}"