I think %opts, in the Makefile.PL, might simply need that amended CCFLAGS entry inserted (anywhere) into it so it looks like this:

my %opts = (
    CCFLAGS => '-D_POSIX_PTHREAD_SEMANTICS -D_REENTRANT -D_LARGEFILE_S
+OURCE -D_FILE_OFFSET_BITS=64',
    NAME   => 'DBI',
    AUTHOR => 'Tim Bunce (dbi-users@perl.org)',
    VERSION_FROM  => 'DBI.pm',
    ABSTRACT_FROM => 'DBI.pm',
    PREREQ_PM => { "Test::Simple" => 0.40, Storable => 1, "File::Spec"
+ => 1 },
    EXE_FILES => [ "dbiproxy$ext_pl", "dbiprof$ext_pl" ],
    DIR => [ ],
    dynamic_lib => { OTHERLDFLAGS => "$::opt_g" },
    clean => { FILES=> "\$(DISTVNAME) Perl.xsi t/zv*_*.t"
            ." dbiproxy$ext_pl dbiprof$ext_pl dbitrace.log dbi.prof nd
+test.prt" },
    dist  => {
    DIST_DEFAULT=> 'clean distcheck disttest tardist',
    PREOP => '$(MAKE) -f Makefile.old distdir',
    COMPRESS => 'gzip -v9', SUFFIX => 'gz',
    },
);
[download]

If that doesn't help try getting a version of gcc that's at least recent enough to either understand or ignore '-fno-strict-aliasing'.

Cheers,
Rob