Build failure of master [MSYS2/Windows]

[Angelo Graziosi <angelo.g0@libero.it>]

As always I tried my monthly build but it fails. The simplest way to reproduce, from a MSYS2/MINGW64 shell

./autogen.sh
[...]
./configure
[...]
make
[...]
  AR       libgnu.a
make[1]: uscita dalla directory "/tmp/emacs-master/lib"
make -C lib-src all
make[1]: ingresso nella directory "/tmp/emacs-master/lib-src"
  CC       ntlib.o
  CCLD     etags.exe
C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: ../lib/libgnu.a(regex.o): in function `init_dfa':
C:\msys64\tmp\emacs-master\lib/regcomp.c:889: undefined reference to `nl_langinfo'
collect2.exe: error: ld returned 1 exit status
make[1]: *** [Makefile:369: etags.exe] Error 1
make[1]: uscita dalla directory "/tmp/emacs-master/lib-src"
make: *** [Makefile:405: lib-src] Error 2

If I try with a parallel build ( make -j2), I see also _a lot a lot_ of this messages


Unescaped left brace in regex is deprecated here (and will be fatal in Perl 5.32), passed through in regex; marked by <-- HERE in m/^\s+@([[:alnum:]][[:alnum:]\-]*)({ <-- HERE })?\s*/ at /usr/share/texinfo/Texinfo/Parser.pm line 5709.
Unescaped left brace in regex is deprecated here (and will be fatal in Perl 5.32), passed through in regex; marked by <-- HERE in m/^\s+@([[:alnum:]][[:alnum:]\-]*)({ <-- HERE })?\s*(\@(c|comment)((\@|\s+).*)?)?/ at /usr/share/texinfo/Texinfo/Parser.pm line 5714.


This is with master 9c022a488bd462b85895ef84313fe84c5bc2bb4d,

Spruce up some regex-emacs comments
* src/regex-emacs.c, src/regex-emacs.h: Update comments.


Notice that the same source (http://git.savannah.gnu.org/cgit/emacs.git/snapshot/emacs-master.tar.gz) builds fine on GNU/Linux and macOS, so the failure seems to concern only Windows.

BTW, GCC on MSYS2/MINGW64 is 

$ gcc -v
Using built-in specs.
COLLECT_GCC=C:\msys64\mingw64\bin\gcc.exe
COLLECT_LTO_WRAPPER=C:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.2.0/lto-wrapper.exe
Target: x86_64-w64-mingw32
[...]
Thread model: posix
gcc version 8.2.0 (Rev1, Built by MSYS2 project)


Ciao,
 Angelo.