r245838: make world fails: /usr/src/usr.bin/dtc/dtc.cc:196:24: error: use of undeclared identifier 'optarg', string arg = string(optarg);

Make world fails in /usr/src/usr.bin/dtc/dtc.cc with a lot of errors
com[laining about an undeclared identifier:

[...]
===> usr.bin/dtc (obj,depend,all,install)
/usr/obj/usr/src/tmp/usr/src/usr.bin/dtc created for /usr/src/usr.bin/dtc
rm -f .depend
mkdep -f .depend -a    -I/usr/obj/usr/src/tmp/legacy/usr/include
-std=c++11  -stdlib=libc++  /usr/src/usr.bin/dtc/dtc.cc
/usr/src/usr.bin/dtc/input_buffer.cc /usr/src/usr.bin/dtc/string.cc
/usr/src/usr.bin/dtc/dtb.cc /usr/src/usr.bin/dtc/fdt.cc
/usr/src/usr.bin/dtc/checking.cc
echo dtc: /usr/lib/libc.a /usr/obj/usr/src/tmp/legacy/usr/lib/libegacy.a
>> .depend
echo dtc: /usr/lib/libc++.a >> .depend
c++ -O2 -pipe -O3 -I/usr/obj/usr/src/tmp/legacy/usr/include
-stdlib=libc++  -std=c++11 -c /usr/src/usr.bin/dtc/dtc.cc
c++ -O2 -pipe -O3 -I/usr/obj/usr/src/tmp/legacy/usr/include
-stdlib=libc++  -std=c++11 -c /usr/src/usr.bin/dtc/input_buffer.cc
/usr/src/usr.bin/dtc/input_buffer.cc:116:11: error: use of undeclared
identifier 'strtoll'
[...]
7 errors generated.
*** [string.o] Error code 1
/usr/src/usr.bin/dtc/input_buffer.cc:218:10: error: use of undeclared
identifier 'stderr'
        fprintf(stderr, "Current cursor: %d\n", cursor);
                ^
/usr/src/usr.bin/dtc/input_buffer.cc:219:42: error: use of undeclared
identifier 'stderr'
        fwrite(&buffer[cursor], size-cursor, 1, stderr);
                                                ^
/usr/src/usr.bin/dtc/input_buffer.cc:227:3: error: use of undeclared
identifier 'perror'
                perror("Failed to stat file");
                ^
/usr/src/usr.bin/dtc/input_buffer.cc:234:3: error: use of undeclared
identifier 'perror'
                perror("Failed to mmap file");
                ^
/usr/src/usr.bin/dtc/input_buffer.cc:249:20: error: use of undeclared
identifier 'stdin'
        while ((c = fgetc(stdin)) != EOF)
                          ^
/usr/src/usr.bin/dtc/input_buffer.cc:249:31: error: use of undeclared
identifier 'EOF'
        while ((c = fgetc(stdin)) != EOF)
                                     ^
15 errors generated.
*** [input_buffer.o] Error code 1
/usr/src/usr.bin/dtc/dtb.cc:87:2: error: use of undeclared identifier
'write'
        write(fd, buffer.data(), buffer.size());
        ^
/usr/src/usr.bin/dtc/dtb.cc:125:2: error: use of undeclared identifier
'snprintf'; did you mean 'vswprintf'?
        snprintf(out, 3, "%.2hhx", b);
        ^~~~~~~~
        vswprintf
/usr/include/wchar.h:130:5: note: 'vswprintf' declared here
int     vswprintf(wchar_t * __restrict, size_t n, const wchar_t *
__restrict,
        ^
/usr/src/usr.bin/dtc/dtb.cc:125:11: error: cannot initialize a parameter
of type 'wchar_t *' with an lvalue of type 'char [3]'
        snprintf(out, 3, "%.2hhx", b);
                 ^~~
/usr/include/wchar.h:130:35: note: passing argument to parameter here
int     vswprintf(wchar_t * __restrict, size_t n, const wchar_t *
__restrict,
                                      ^
/usr/src/usr.bin/dtc/dtb.cc:218:2: error: use of undeclared identifier
'write'
        write(fd, buffer.data(), buffer.size());
        ^
/usr/src/usr.bin/dtc/dtb.cc:259:11: error: use of undeclared identifier
'stderr'
                fprintf(stderr, "Missing magic token in header.  Got %"
PRIx32
                        ^
5 errors generated.
*** [dtb.o] Error code 1
/usr/src/usr.bin/dtc/dtc.cc:102:15: error: use of undeclared identifier
'getopt'
        while ((ch = getopt(argc, argv, options)) != -1)
[...]