[Bug driver/49371] New: xgcc: error: unrecognized option '-pie' on *-apple-darwin*

["dominiq at lps dot ens.fr" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49371

           Summary: xgcc: error: unrecognized option '-pie' on
                    *-apple-darwin*
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: driver
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dominiq@lps.ens.fr
                CC: mikestump@comcast.net, joseph@codesourcery.com,
                    ro@CeBiTec.Uni-Bielefeld.DE, iains@gcc.gnu.org
              Host: *-apple-darwin*
            Target: *-apple-darwin*
             Build: *-apple-darwin*


On *-apple-darwin* revisions 174909 and 174910 introduced several failures in
gcc.dg/torture/tls/* with '-pie -fPIE' (see
http://gcc.gnu.org/ml/gcc-testresults/2011-06/msg01259.html ). The errors are
all (AFAICT) of the kind.

FAIL: gcc.dg/torture/tls/thr-init-1.c  -O0  -pie -fpie  (test for excess
errors)
Excess errors:
xgcc: error: unrecognized option '-pie'

My understanding of -pie is that it is a linker option supported by
*-apple-darwin9 and later. Apparently this option is not recognized by gcc
since at least version 4.4.4, this is why I mark this PR as a driver one
(please change it if you disagree).

A short term fix will be to remove darwin from 

proc check_effective_target_pie { } {
    if { [istarget *-*-darwin\[912\]*]
     || [istarget *-*-linux*] } {
    return 1;
    }
    return 0
}

in gcc/testsuite/lib/target-supports.exp, but I think the darwin driver should
be fixed.