ld: Fix pr22269-1 on 32-bit Solaris/SPARC

[Jose E. Marchesi]

    pr22269-1.s currently FAILs to assemble on 32-bit Solaris/SPARC:
    
    ERROR:  -K PIC tmpdir/pr22269-1.s: assembly failed
    UNRESOLVED: pr22269-1 (static pie undefined weak)
    
    tmpdir/pr22269-1.s: Assembler messages:
    tmpdir/pr22269-1.s:27: Error: Architecture mismatch on "be,pn %icc,.LL4 ,pn %icc,.LL4".
    tmpdir/pr22269-1.s:27: (Requires v9|v9a|v9b|v9c|v9d|v9e|v9v|v9m|m8; requested architecture is sparclite.)
    tmpdir/pr22269-1.s:32: Error: Architecture mismatch on "return %i7+8".
    tmpdir/pr22269-1.s:32: (Requires v9|v9a|v9b|v9c|v9d|v9e|v9v|v9m|m8; requested architecture is sparclite.)
    tmpdir/pr22269-1.s:36: Error: Architecture mismatch on "return %i7+8".
    tmpdir/pr22269-1.s:36: (Requires v9|v9a|v9b|v9c|v9d|v9e|v9v|v9m|m8; requested architecture is sparclite.)
    
    I could trace this to the fact that gcc on sparc-sun-solaris2.* defaults
    to --with-cpu=v9.  So the gcc -S step of compiling the testcase is run
    with -mcpu=v9, while the manual invocation of as-new lacks the
    corresponding -Av9, creating a mismatch.
    
    Solaris seems to be the only affected target, otherwise only
    64-bit-default configurations default to --with-cpu=v9 or
    --with-cpu=ultrasparc: sparcv9-*-*, sparc64-*-*,
    sparc64-*-freebsd*, ultrasparc-*-freebsd*, and sparc64-*-openbsd*.
    
    I see two possible solutions:
    
    * Don't invoke as-new directly, but let gcc do it so the compiler and
      assembler options match, just as is done for ld-new invocations via
      the symlinks in ld/tmpdir/ld where an as symlink is already created.
      However, one would have to prefix all assembler options with -Wa, to
      get them through the compiler driver and one has less control over the
      as-new invocations due to what gcc passes on its own.
    
    * Alternatively, one could just add -Av9 to AFLAGS_PIC in
      ld-elf/shared.exp and be done with it.  While less general than the
      first option, it has a precedent in ld-elfvers/vers.exp where -Av9a is
      added to as_options on sparc-*-*.  I can't tell if there's a downside
      to that solution.
    
    The patch below implements the second alternative.  It lets the test
    pass and causes no other changes in sparc-sun-solaris2.11 test results.
    
    Ok for master?
    
Looks like a good solution to me.