Using 64-bit Ruby installer from rubyinstaller.org with DevKit.

Here's what I see when I run bundle install:

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

current directory: C:/ruby23/lib/ruby/gems/2.3.0/gems/bson-4.2.1/ext/bson
C:/ruby23/bin/ruby.exe -r ./siteconf20170213-1444-1kvewcr.rb extconf.rb
creating Makefile

current directory: C:/ruby23/lib/ruby/gems/2.3.0/gems/bson-4.2.1/ext/bson
make "DESTDIR=" clean
0 [main] us 0 init_cheap: VirtualAlloc pointer is null, Win32 error 487
AllocationBase 0x0, BaseAddress 0x60E90000, RegionSize 0x490000, State 0x10000
C:\ruby23\devkit\bin\make.exe: *** Couldn't reserve space for cygwin's heap,
Win32 error 0

current directory: C:/ruby23/lib/ruby/gems/2.3.0/gems/bson-4.2.1/ext/bson
make "DESTDIR="
0 [main] us 0 init_cheap: VirtualAlloc pointer is null, Win32 error 487
AllocationBase 0x0, BaseAddress 0x60E90000, RegionSize 0x490000, State 0x10000
C:\ruby23\devkit\bin\make.exe: *** Couldn't reserve space for cygwin's heap,
Win32 error 0

make failed, exit code 1

Gem files will remain installed in C:/ruby23/lib/ruby/gems/2.3.0/gems/bson-4.2.1
for inspection.
Results logged to
C:/ruby23/lib/ruby/gems/2.3.0/extensions/x64-mingw32/2.3.0/bson-4.2.1/gem_make.out

An error occurred while installing bson (4.2.1), and Bundler cannot continue.
Make sure that `gem install bson -v '4.2.1'` succeeds before bundling.

Process finished with exit code 5