How to include mruby after installing with rbenv/ruby-build?

I'm trying to compile the "Source Code (.c)" example from this tutorial.

I have installed mruby using rbenv: rbenv install mruby-1.2.0

I get an error when trying to compile the program:

$ gcc -std=c99 -Imruby/include test_program.c -o test_program

test_program.c:1:10: fatal error: 'mruby.h' file not found
#include "mruby.h"
         ^
1 error generated.

How am I supposed to reference the mruby library when installing via rbenv/ruby-build?

Solution

Seems like rbenv install mruby-1.2.0 doesn't install header files of mruby(it's only a dump of build/host directory after mruby is built):

% ls $(rbenv prefix mruby-1.2.0)
LEGAL   bin     lib     mrbgems mrblib  src

You need

# get mruby's code
git clone https://github.com/mruby/mruby.git mruby
# build mruby
cd mruby && rake
# go back to directory of `test_program.c`
cd ..

before test_program.c's compilation instead. And you need mruby/build/host/lib/libmruby.a -lm compile options too.