gem install failure under MSYS2, confuses MSYS with Linux/Cygwin?

[Jodocus]

When trying to install the json gem via gem install json, I get

Building native extensions.  This could take a while...
ERROR:  Error installing json:
    ERROR: Failed to build gem native extension.

current directory: /home/<...>/.gem/ruby/2.3.0/gems/json-2.0.3/ext/json/ext/generator/usr/bin/ruby.exe -r ./siteconf20170404-3632-18oxo5w.rb extconf.rb
creating Makefile

current directory: /home/<...>/.gem/ruby/2.3.0/gems/json-2.0.3/ext/json/ext/generator
make "DESTDIR=" clean
rm -f
rm -f generator.so  *.o  *.bak mkmf.log .*.time

current directory: /home/<...>/.gem/ruby/2.3.0/gems/json-2.0.3/ext/json/ext/generator
make "DESTDIR="
gcc -I. -I/usr/include/ruby-2.3.0/x86_64-msys -I/usr/include/ruby-2.3.0/ruby/backward -I/usr/include/ruby-2.3.0 -I. -DJSON_GENERATOR -D_FORTIFY_SOURCE=2    -march=x86-64 -mtune=generic -O2 -pipe -fno-strict-aliasing   -o generator.o -c generator.c
In file included from C:/util/msys64/usr/include/ruby-2.3.0/ruby/ruby.h:36:0,
             from C:/util/msys64/usr/include/ruby-2.3.0/ruby.h:33,
             from ../fbuffer/fbuffer.h:5,
             from generator.c:1:
C:/util/msys64/usr/include/ruby-2.3.0/ruby/defines.h:61:25: fatal error: sys/select.h: No such file or directory
 # include <sys/select.h>
                     ^
compilation terminated.
make: *** [Makefile:239: generator.o] Fehler 1

make failed, exit code 2

Gem files will remain installed in /home/<...>/.gem/ruby/2.3.0/gems/json-2.0.3 for inspection.
Results logged to /home/<...>/.gem/ruby/2.3.0/extensions/x86_64-msys/2.3.0/json-2.0.3/gem_make.out

There is no <sys/select.h> on Windows/MSYS2. What can I do about it?

[MSP-Greg]

@Jodocus

The gem will install with RubyInstaller2 (or similar) builds. Appveyor results here.

I believe the ragel package needs to be installed.

[hsbt]

I could install json-2.6.3 with RubyInstaller2 + devkit.