gem install 'bycrpt' => BOOOOMMMMM

gistfile1.txt

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