error occurred while installing crypt (3.1.7) - ruby

Question

I have an error message while running sudo bundle install:
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
checking for ruby/util.h... yes
creating Makefile
make "DESTDIR=" clean
make "DESTDIR="
compiling bcrypt_ext.c
compiling crypt.c
compiling crypt_blowfish.c
compiling crypt_gensalt.c
compiling wrapper.c
linking shared-object bcrypt_ext.bundle
clang: error: unknown argument: '-multiply_definedsuppress' [-Wunused-command-line-argument-hard-error-in-future]
clang: note: this will be a hard error (cannot be downgraded to a warning) in the future
make: *** [bcrypt_ext.bundle] Error 1
make failed, exit code 2
Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/bcrypt-3.1.7 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-13/2.0.0/bcrypt-3.1.7/gem_make.out
An error occurred while installing bcrypt (3.1.7), and Bundler cannot continue.
Make sure that `gem install bcrypt -v '3.1.7'` succeeds before bundling.
Then I tried to run sudo gem install bcrypt -v '3.1.7' and have below error message:
Building native extensions. This could take a while...
ERROR: Error installing bcrypt:
ERROR: Failed to build gem native extension.
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
checking for ruby/util.h... yes
creating Makefile
make "DESTDIR=" clean
make "DESTDIR="
compiling bcrypt_ext.c
compiling crypt.c
compiling crypt_blowfish.c
compiling crypt_gensalt.c
compiling wrapper.c
linking shared-object bcrypt_ext.bundle
clang: error: unknown argument: '-multiply_definedsuppress' [-Wunused-command-line-argument-hard-error-in-future]
clang: note: this will be a hard error (cannot be downgraded to a warning) in the future
make: *** [bcrypt_ext.bundle] Error 1
make failed, exit code 2
Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/bcrypt-3.1.7 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-13/2.0.0/bcrypt-3.1.7/gem_make.out
After this, I try to run sudo gem install bcrypt, still not working. Any tips?

Answer 1

I had upgraded Xcode from the Mac App Store, and that caused this particular error for me.
The way to fix it in my case: run Xcode and accept the license terms, etc. Then when I ran bundle install, it compiled and installed bcrypt just fine.