Compile error on cygwin with strerror_r - cygwin

Question

I am getting a build error using make:
g++ -std=c++11 -DHAVE_CONFIG_H -I. -I../src/config -I. -I./obj -DBOOST_SP_USE_STD_ATOMIC -DBOOST_
AC_USE_STD_ATOMIC -pthread -I/usr/include -I./leveldb/include -I./leveldb/helpers/memenv -I./secp2
56k1/include -I./univalue/include -DHAVE_BUILD_INFO -D__STDC_FORMAT_MACROS -std=c99 -D_XOPEN_SOURCE=
500 -g -O2 -Wall -Wextra -Wformat -Wvla -Wformat-security -Wno-unused-parameter -MT libbitcoin_co
mmon_a-netbase.o -MD -MP -MF .deps/libbitcoin_common_a-netbase.Tpo -c -o libbitcoin_common_a-netbase
.o `test -f 'netbase.cpp' || echo './'`netbase.cpp
cc1plus: warning: command line option `-std=c99' is valid for C/ObjC but not for C++
In file included from /usr/include/boost/assert.hpp:58:0,
from /usr/include/boost/range/size.hpp:23,
from /usr/include/boost/range/functions.hpp:20,
from /usr/include/boost/range/iterator_range_core.hpp:38,
from /usr/include/boost/range/iterator_range.hpp:13,
from /usr/include/boost/range/as_literal.hpp:22,
from /usr/include/boost/algorithm/string/case_conv.hpp:19,
from netbase.cpp:25:
netbase.cpp: In function `bool LookupIntern(const char*, std::vector<CNetAddr>&, unsigned int, bool)
':
netbase.cpp:95:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compa
re]
assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in));
~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
netbase.cpp:101:39: warning: comparison between signed and unsigned integer expressions [-Wsign-comp
are]
assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in6));
~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
netbase.cpp: In function `std::string NetworkErrorString(int)':
netbase.cpp:720:41: error: `strerror_r' was not declared in this scope
if (strerror_r(err, buf, sizeof(buf)))
^
^
Evidently cygwin does support strerror_r as per https://cygwin.com/cygwin-api/compatibility.html#std-susv4
Code snippet where the code is breaking:
#ifdef STRERROR_R_CHAR_P /* GNU variant can return a pointer outside the passed buffer */
s = strerror_r(err, buf, sizeof(buf));
#else /* POSIX variant always returns message in buffer */
s = buf;
if (strerror_r(err, buf, sizeof(buf)))
buf[0] = 0;
#endif
Can someone guide me as to how I can fix this ?
TIA