When I try to build vim(8.1.0509) with ruby support(--enable-rubyinterp) on macOS Mojave(10.14.1) I get error:
In file included from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0/ruby.h:33:
/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0/ruby/ruby.h:24:10: fatal error:
'ruby/config.h' file not found
#include "ruby/config.h"
I have installed Xcode 10.1.
xcode-select -p
/Applications/Xcode.app/Contents/Developer
My problem was different from - Yosemite upgrade broke ruby.h
As you can see in the description of the problem it's System's ruby, not Xcode's ruby so reinstall Xcode or symlink didn't help here.
Answer: I have reinstalled macOS Mojave without losing any data and this fixed the problem.