Fix: [Cygwin] Fix missing AI_ADDRCONFIG declaration

Fixes the following complaints:

src/network/core/address.cpp: In member function 'const sockaddr_storage* NetworkAddress::GetAddress()':
src/network/core/address.cpp:134:55: error: 'AI_ADDRCONFIG' was not declared in this scope
   this->Resolve(this->address.ss_family, SOCK_STREAM, AI_ADDRCONFIG, nullptr, ResolveLoopProc);

Signed-off-by: Joe Stringer <joe@wand.net.nz>

src/network/core/os_abstraction.h

@@ -31,6 +31,11 @@
 /* Windows has some different names for some types */
 typedef unsigned long in_addr_t;
 
+/* Handle cross-compilation with --build=*-*-cygwin --host=*-*-mingw32 */
+#if defined(__MINGW32__) && !defined(AI_ADDRCONFIG)
+#	define AI_ADDRCONFIG               0x00000400
+#endif
+
 #if !(defined(__MINGW32__) || defined(__CYGWIN__))
 	/* Windows has some different names for some types */
 	typedef SSIZE_T ssize_t;