Flang arg_parser fails to accept input on stdin

[kiranchandramohan]

Flang does not accept input on stdin. It generates an error.
For e.g : flang -o - -S -x f95 - < ex.f90
F90-F-0000-Internal compiler error. Unknown command line argument: 0

function f(a)
  real a
  f = a*a
  return
end

While the eqiuvalent clang command works fine and generates assembly.
For e.g : clang -o - -S -x c - < ex.c

float f(float a)
{
  return a*a;
}