Can't install gem under Ruby 2.1.7

[mentiflectax]

When I run gem install thin under Ruby 2.1.7 (ruby 2.1.7p400 (2015-08-18 revision 51632) [i386-mingw32]), I get following errors.

D:\dev\derek\50web>gem install thin
Building native extensions.  This could take a while...
ERROR:  Error installing thin:
        ERROR: Failed to build gem native extension.

    C:/Ruby21/bin/ruby.exe extconf.rb
checking for main() in -lssleay32... no
checking for main() in -lssleay32... no
checking for main() in -lssleay32... no
checking for main() in -lssleay32... no
checking for rb_trap_immediate in ruby.h,rubysig.h... no
checking for rb_thread_blocking_region()... yes
checking for ruby/thread.h... yes
checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
checking for inotify_init() in sys/inotify.h... no
checking for __NR_inotify_init in sys/syscall.h... no
checking for writev() in sys/uio.h... no
checking for rb_thread_fd_select()... yes
checking for rb_fdset_t in ruby/intern.h... yes
checking for pipe2() in unistd.h... no
checking for accept4() in sys/socket.h... no
checking for SOCK_CLOEXEC in sys/socket.h... no
checking for rb_wait_for_single_fd()... yes
checking for rb_enable_interrupt()... no
checking for rb_time_new()... yes
checking for windows.h... yes
checking for winsock.h... yes
checking for main() in -lkernel32... yes
checking for main() in -lrpcrt4... yes
checking for main() in -lgdi32... yes
checking for clock_gettime()... yes
checking for CLOCK_MONOTONIC_RAW in time.h... no
checking for CLOCK_MONOTONIC in time.h... yes
CXXFLAGS=$(cxxflags) -Wall -Wextra -Wno-deprecated-declarations -Wno-ignored-qua
lifiers -Wno-unused-result -Wno-address
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
generating rubyeventmachine-i386-mingw32.def
compiling binder.cpp
compiling cmain.cpp
cmain.cpp: In function 'int evma_send_file_data_to_connection(uintptr_t, const c
har*)':
cmain.cpp:802:20: error: 'fstat' was not declared in this scope
  if (fstat (Fd, &st)) {
                    ^
make: *** [cmain.o] Error 1

make failed, exit code 2

Gem files will remain installed in C:/Ruby21/lib/ruby/gems/2.1.0/gems/eventmachi
ne-1.0.9.1 for inspection.
Results logged to C:/Ruby21/lib/ruby/gems/2.1.0/extensions/x86-mingw32/2.1.0/eve
ntmachine-1.0.9.1/gem_make.out

D:\dev\derek\50web>

C:/Ruby21/lib/ruby/gems/2.1.0/extensions/x86-mingw32/2.1.0/eventmachine-1.0.9.1/gem_make.out:

C:/Ruby21/bin/ruby.exe extconf.rb
checking for main() in -lssleay32... no
checking for main() in -lssleay32... no
checking for main() in -lssleay32... no
checking for main() in -lssleay32... no
checking for rb_trap_immediate in ruby.h,rubysig.h... no
checking for rb_thread_blocking_region()... yes
checking for ruby/thread.h... yes
checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
checking for inotify_init() in sys/inotify.h... no
checking for __NR_inotify_init in sys/syscall.h... no
checking for writev() in sys/uio.h... no
checking for rb_thread_fd_select()... yes
checking for rb_fdset_t in ruby/intern.h... yes
checking for pipe2() in unistd.h... no
checking for accept4() in sys/socket.h... no
checking for SOCK_CLOEXEC in sys/socket.h... no
checking for rb_wait_for_single_fd()... yes
checking for rb_enable_interrupt()... no
checking for rb_time_new()... yes
checking for windows.h... yes
checking for winsock.h... yes
checking for main() in -lkernel32... yes
checking for main() in -lrpcrt4... yes
checking for main() in -lgdi32... yes
checking for clock_gettime()... yes
checking for CLOCK_MONOTONIC_RAW in time.h... no
checking for CLOCK_MONOTONIC in time.h... yes
CXXFLAGS=$(cxxflags) -Wall -Wextra -Wno-deprecated-declarations -Wno-ignored-qualifiers -Wno-unused-result -Wno-address
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
generating rubyeventmachine-i386-mingw32.def
compiling binder.cpp
compiling cmain.cpp
cmain.cpp: In function 'int evma_send_file_data_to_connection(uintptr_t, const char*)':
cmain.cpp:802:20: error: 'fstat' was not declared in this scope
  if (fstat (Fd, &st)) {
                    ^
make: *** [cmain.o] Error 1

make failed, exit code 2

[mentiflectax]

You can StackOverflow reputation points by answering a question about this issue there - http://stackoverflow.com/questions/35069733/how-can-i-work-around-installation-error-of-thin-gem .

[mentiflectax]

I fixed the error by installing DevKit.