Building rtems toolchain with fortran support error

[Ricardo Derbes]

Hello.
I'm trying to build rtems toolchain for i386 using
rtems-source-builder with fortran support (--with-fortran option).
The RSB I'm using has been dowloaded from git, commit
534332f22a66f16b4022e87ae50c11ff20c98dcb from Sep 12 2016.

The full command line is:
../source-builder/sb-set-builder
--prefix=~/devel4.12-i386.fortran/rtems4.12 4.12/rtems-i386
--without-rtems --with-fortran

When trying to build gcc, it fails with the following errors (excerpt
from report file
rsb-report-i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1.txt):

Tail of the build log:
~/devel4.12-i386.fortran/rtems-source-builder/rtems/build/i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1/gcc-6-20160609/newlib/libc/include/ieeefp.h:196:38:
error: 'EXT_FRACHBITS' undeclared here (not in a function)
__ieee_ext_field_type  ext_frach : EXT_FRACHBITS;
                                      ^~~~~~~~~~~~~
~/devel4.12-i386.fortran/rtems-source-builder/rtems/build/i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1/gcc-6-20160609/newlib/libc/include/ieeefp.h:196:26:
error: bit-field 'ext_frach' width not an integer constant
__ieee_ext_field_type  ext_frach : EXT_FRACHBITS;
                          ^~~~~~~~~
/home/dev/devel4.12-i386.fortran/rtems-source-builder/rtems/build/i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1/gcc-6-20160609/newlib/libc/include/ieeefp.h:197:3:
error: unknown type name '__ieee_ext_field_type'
   __ieee_ext_field_type  ext_exp   : EXT_EXPBITS;
   ^~~~~~~~~~~~~~~~~~~~~
~/devel4.12-i386.fortran/rtems-source-builder/rtems/build/i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1/gcc-6-20160609/newlib/libc/include/ieeefp.h:197:38:
error: 'EXT_EXPBITS' undeclared here (not in a function)
__ieee_ext_field_type  ext_exp   : EXT_EXPBITS;
                                      ^~~~~~~~~~~
/home/dev/devel4.12-i386.fortran/rtems-source-builder/rtems/build/i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1/gcc-6-20160609/newlib/libc/include/ieeefp.h:197:26:
error: bit-field 'ext_exp' width not an integer constant
__ieee_ext_field_type  ext_exp   : EXT_EXPBITS;
                          ^~~~~~~
~/devel4.12-i386.fortran/rtems-source-builder/rtems/build/i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1/gcc-6-20160609/newlib/libc/include/ieeefp.h:198:3:
error: unknown type name '__ieee_ext_field_type'
__ieee_ext_field_type  ext_sign  : 1;
   ^~~~~~~~~~~~~~~~~~~~~

As for my application I need fortran support, how can I fix this problem?
As long I can see, all symbols that the compiler claims as undeclared
are indeed declared and accessible in file
~/devel4.12-i386.fortran/rtems-source-builder/rtems/build/i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1/gcc-6-20160609/newlib/libc/include/ieeefp.h
May be it's missing a symbol, e.g a proper value for LDBL_MANT_DIG ?

Thank you