[Bug bootstrap/65537] New: [5 Regression]: --with-build-config=bootstrap-lto fails on CentOS 5.11

["ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65537

            Bug ID: 65537
           Summary: [5 Regression]: --with-build-config=bootstrap-lto
                    fails on CentOS 5.11
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: bootstrap
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ubizjak at gmail dot com

When configured with --with-build-config=bootstrap-lto, the bootstrap fails on
CentOS 5.11 in libiberty with:

/home/uros/gcc-build/./prev-gcc/gcc-ar -B/home/uros/gcc-build/./prev-gcc/ rc
./libiberty.a \
          ./regex.o ./cplus-dem.o ./cp-demangle.o ./md5.o ./sha1.o ./alloca.o
./argv.o ./choose-temp.o ./concat.o ./cp-demint.o ./crc32.o ./d-demangle.o
./dwarfnames.o ./dyn-string.o ./fdmatch.o ./fibheap.o ./filename_cmp.o
./floatformat.o ./fnmatch.o ./fopen_unlocked.o ./getopt.o ./getopt1.o
./getpwd.o ./getruntime.o ./hashtab.o ./hex.o ./lbasename.o ./lrealpath.o
./make-relative-prefix.o ./make-temp-file.o ./objalloc.o ./obstack.o
./partition.o ./pexecute.o ./physmem.o ./pex-common.o ./pex-one.o ./pex-unix.o
./vprintf-support.o ./safe-ctype.o ./simple-object.o ./simple-object-coff.o
./simple-object-elf.o ./simple-object-mach-o.o ./simple-object-xcoff.o ./sort.o
./spaces.o ./splay-tree.o ./stack-limit.o ./strerror.o ./strsignal.o
./timeval-utils.o ./unlink-if-ordinary.o ./xasprintf.o ./xatexit.o ./xexit.o
./xmalloc.o ./xmemdup.o ./xstrdup.o ./xstrerror.o ./xstrndup.o ./xvasprintf.o 
./mkstemps.o ./setproctitle.o
/usr/bin/ar: illegal option -- -
Usage: /usr/bin/ar [emulation options] [-]{dmpqrstx}[abcfilNoPsSuvV]
[member-name] [count] archive-file file...
       /usr/bin/ar -M [<mri-script]
 commands:
  d            - delete file(s) from the archive
  m[ab]        - move file(s) in the archive
  p            - print file(s) found in the archive
  q[f]         - quick append file(s) to the archive
  r[ab][f][u]  - replace existing or insert new file(s) into the archive
  t            - display contents of archive
  x[o]         - extract file(s) from the archive
 command specific modifiers:
  [a]          - put file(s) after [member-name]
  [b]          - put file(s) before [member-name] (same as [i])
  [N]          - use instance [count] of name
  [f]          - truncate inserted file names
  [P]          - use full path names when matching
  [o]          - preserve original dates
  [u]          - only replace files that are newer than current archive
contents
 generic modifiers:
  [c]          - do not warn if the library had to be created
  [s]          - create an archive index (cf. ranlib)
  [S]          - do not build a symbol table
  [v]          - be verbose
  [V]          - display the version number
  @<file>      - read options from <file>
 emulation options: 
  No emulation specific options
/usr/bin/ar: supported targets: elf64-x86-64 elf32-i386 a.out-i386-linux
efi-app-ia32 elf64-little elf64-big elf32-little elf32-big srec symbolsrec
tekhex binary ihex
gmake[3]: *** [libiberty.a] Error 1
gmake[3]: Leaving directory `/home/uros/gcc-build/libiberty'
gmake[2]: *** [all-stage2-libiberty] Error 2
gmake[2]: Leaving directory `/home/uros/gcc-build'
gmake[1]: *** [stage2-bubble] Error 2
gmake[1]: Leaving directory `/home/uros/gcc-build'
gmake: *** [all] Error 2

The problem is with gcc-ar that unconditionally passes --plugin option to ar. 
This fails on older binutils, such as:

$ ar --version
GNU ar 2.17.50.0.6-26.el5 20061020
Copyright 2005 Free Software Foundation, Inc.

LTO bootstrap worked a while ago, so this is a regression on 5.0 branch.