Failure building Emacs from master

[Angelo Graziosi]

Current master (c265febd97e940e6580ae42aa648358a0a2ed830) fails to build 
(at least on MSYS2/UCRT64):

[...]
  GEN      ../../etc/charsets/JISX0212.map
  CC       timefns.o
  CC       atimer.o
process.c:41:10: fatal error: netinet/tcp.h: No such file or directory
   41 | #include <netinet/tcp.h>
      |          ^~~~~~~~~~~~~~~
compilation terminated.
  GEN      ../../etc/charsets/JISX2132.map
make[1]: *** [Makefile:457: process.o] Error 1
make[1]: *** Attesa per i processi non terminati....
[...]


Ciao,
   Angelo.