Suddenly failing `rvm install`command on os x 10.11 (El Capitan)

This actually started with a strange error, when I went to fire up a rails server in an app I’d been working on the night before.

Unable to load application: LoadError: dlopen(/Users/xxx/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/x86_64-darwin14/readline.bundle, 9): Library not loaded: /usr/local/opt/readline/lib/libreadline.6.dylib

Like I mentioned, I’d fired up this app less than 24 hours prior, so this was very strange to me. Some quick googling around suggested that I try to reinstall my ruby version so I ran the command

rvm reinstall 2.3.0

Well that errored out with another strange error

ruby-2.3.0 - #configuring...........................................................
ruby-2.3.0 - #post-configuration.
ruby-2.3.0 - #compiling...........
Error running '__rvm_make -j 1',
showing last 15 lines of /Users/xxx/.rvm/log/1476345601_ruby-2.3.0/make.log
compiling enc/trans/newline.c
compiling ./missing/explicit_bzero.c
compiling ./missing/setproctitle.c
compiling dmyenc.c
linking miniruby
dyld: lazy symbol binding failed: Symbol not found: _clock_gettime
  Referenced from: /Users/xxx/.rvm/src/ruby-2.3.0/./miniruby (which was built for Mac OS X 10.12)
  Expected in: /usr/lib/libSystem.B.dylib
dyld: Symbol not found: _clock_gettime
  Referenced from: /Users/xxx/.rvm/src/ruby-2.3.0/./miniruby (which was built for Mac OS X 10.12)
  Expected in: /usr/lib/libSystem.B.dylib
make: *** [.rbconfig.time] Trace/BPT trap: 5
++ return 2
There has been an error while running make. Halting the installation.

You might notice the “(which was built for Mac OS X 10.12)
which is a bit of a hint at what the problem is.

Because the last line hints the problem is with make, I decided to reinstall make with brew and it dumped the solution to the problem in my lap

brew install make
Warning: You have Xcode 8 installed without the CLT;
this causes certain builds to fail on OS X El Capitan (10.11).
Please install the CLT via:
sudo xcode-select --install

Basically I’d upgraded my Xcode version without installing command line tools. Once I ran this command, my rvm reinstall went fine and my readline problems went away.