The compiler failed to generate an executable file. (RuntimeError)

Be sure to open XCode after updates. I found that I had to open it and accept the new license agreement after a recent update of XCode via the App Store. Otherwise I received the "The compiler failed to generate an executable file. (RuntimeError) You have to install development tools first."

Same problem occurred and I finally solved it. Here are the steps I followed:

• Xcode, Xcode CLT
• sudo xcodebuild -license
• sudo port upgrade outdated
• sudo port install apple-gcc42
• rvm reinstall 1.9.3 #important!

Really, I think just first,second and last steps required, but can not test it.