Ruby build failed with rbenv - cannot locate make? - ruby

Question

I have just wasted 2 days of my life trying to figure this out, and I need some help please!
I am a complete noob to ruby, and all I want to do is install octopress so that I can have a blog. I think I messed up my mac dev environment somehow - when I try to install ruby with rbenv, it fails and tells me that it cannot find make? How do I fix this?
Thanks for your help in advance.
Mike
Installing ruby-2.4.0...
BUILD FAILED (OS X 10.12.3 using ruby-build 20170201)
Inspect or clean up the working tree at /var/folders/d7/xhd01lr92rvglw0vw9hzkx1m0000gn/T/ruby-build.20170214143528.84918
Results logged to /var/folders/d7/xhd01lr92rvglw0vw9hzkx1m0000gn/T/ruby-build.20170214143528.84918.log
Last 10 log lines:
checking for sigsetjmp as a macro or function... yes
checking for setjmp type... _setjmp
checking for prefix of external symbols... _
checking pthread.h usability... yes
checking pthread.h presence... yes
checking for pthread.h... yes
checking if make is GNU make... ./configure: /usr/local/bin/make: /usr/local/opt/ruby/bin/ruby: bad interpreter: No such file or directory
no
checking for safe null command for make... configure: error: no candidate for safe null command
/usr/local/bin/ruby-build: /usr/local/bin/make: /usr/local/opt/ruby/bin/ruby: bad interpreter: No such file or directory
Here is the output of the following commands:
$ which ruby
/usr/bin/ruby
head /usr/local/bin/make
#!/usr/local/opt/ruby/bin/ruby
#
# This file was generated by RubyGems.
#
# The application 'make' is installed as part of a gem, and
# this file is here to facilitate running it.
#
require 'rubygems'
And here is the output of echo $PATH:
/Users/michaelhenry/.rbenv/shims:/Users/michaelhenry/.rbenv/bin:/usr/local/bin:/Users/michaelhenry/.rbenv/shims:/Users/michaelhenry/.rbenv/bin:/usr/local/Cellar/coreutils/8.26/libexec/gnubin:/usr/local/bin:/usr/local/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Frameworks/Mono.framework/Versions/Current/Commands