title: flang can not find iso_c_bindings while encapsulating a C function from a static library
body: <p>I have a static library named <code>mylib.a</code> written in C and I am trying to do my first call to C from Fortran.</p>
  <p>I want to invoke in Fortran the following function contained in the C library:</p>
  <pre><code>double get_step(double value); 
  </code></pre>
  <p>I try the following Fortran code:</p>
  <pre><code>! TEST FORTRAN WRAPPER
  
  module test
  
          use, intrinsic  :: iso_c_binding
  
          ! Interface to C routine
          ! double get_step(double value);
          interface
                  real(c_double) function _get_step(value) bind(C, 'get_step')
                          use, intrinsic :: iso_c_binding, only : c_double
                          real(c_double) :: value
                  end function
          end interface
  
  end module
  </code></pre>
  <p>I try to compile it like this:</p>
  <pre><code>$ flang test.f90 mylib.a
  F90-F-0004-Unable to open MODULE file iso_c_binding.mod (test.f90: 5)
  F90/x86-64 FreeBSD Flang - 1.5 2017-05-01: compilation aborted
  </code></pre>
  <ul>
  <li>What am I doing wrong?</li>
  <li>Can I use the same name <code>get_step</code> for the Fortran function?</li>
  </ul>