Bummer, can't debug ieee_selected_real_kind

[Steve Kargl]

It seems someone hase broken the ability to use a debugger
with f951 if the Fortran includes 'use ieee_arithmetic'

% gdb82 ~/work/libexec/gcc/i586-unknown-freebsd13.0/9.0.0/f951
 b simplify.c:5836
Breakpoint 1 at 0x843bd8d: file ../../gcc/gcc/fortran/simplify.c, line 5837.
(gdb) run a.f90
Starting program: /usr/home/kargl/work/libexec/gcc/i586-unknown-freebsd13.0/9.0.0/f951 a.f90
a.f90:3:7:

    3 |    use ieee_arithmetic
      |       1
Fatal Error: Can't open module file 'ieee_arithmetic.mod' for reading at (1): No such file or directory
compilation terminated.

-- 
Steve