Recent change breaking most *-elf newlib targets

This change:

commit d4f4e7ae1be1bcf8c021f2b0865aafc16b338aa3 (HEAD)
Author: Takashi Yano <[email protected]>
Date:   Tue Jul 3 18:04:31 2018 +0900

    Fix a bug of perror()/psignal() that changes the orientation of stderr.

    * perror.c: Fix the problem that perror() changes the orientation
      of stderr to byte-oriented mode if stderr is not oriented yet.
    * psignal.c: Ditto.

Introduced "#include <sys/uio.h>

Most *-elf newlib targets are now failing with:

fr30-elf-gcc
-B/opt/notnfs/law/jenkins/workspace/fr30-elf/fr30-elf-obj/newlib/fr30-elf/newlib/
-isystem
/opt/notnfs/law/jenkins/workspace/fr30-elf/fr30-elf-obj/newlib/fr30-elf/newlib/targ-include
-isystem
/opt/notnfs/law/jenkins/workspace/fr30-elf/newlib/newlib/libc/include
-B/opt/notnfs/law/jenkins/workspace/fr30-elf/fr30-elf-obj/newlib/fr30-elf/libgloss/fr30
-L/opt/notnfs/law/jenkins/workspace/fr30-elf/fr30-elf-obj/newlib/fr30-elf/libgloss/libnosys
-L/opt/notnfs/law/jenkins/workspace/fr30-elf/newlib/libgloss/fr30
-DPACKAGE_NAME=\"newlib\" -DPACKAGE_TARNAME=\"newlib\"
-DPACKAGE_VERSION=\"3.0.0\" -DPACKAGE_STRING=\"newlib\ 3.0.0\"
-DPACKAGE_BUGREPORT=\"\" -DPACKAGE_URL=\"\" -I.
-I../../../../../../newlib/newlib/libc/signal -fno-builtin      -g -O2
-g -Os -c -o lib_a-signal.o `test -f 'signal.c' || echo
'../../../../../../newlib/newlib/libc/signal/'`signal.c
../../../../../../newlib/newlib/libc/signal/psignal.c:35:10: fatal
error: sys/uio.h: No such file or directory
 #include <sys/uio.h>
          ^~~~~~~~~~~
compilation terminated.
Makefile:346: recipe for target 'lib_a-psignal.o' failed
make[5]: *** [lib_a-psignal.o] Error 1
make[5]: *** Waiting for unfinished jobs....