Do not rely on ebl_check_special_section when checking debuginfo files.

Do not rely on ebl_check_special_section when checking debuginfo files.

The test run-strip-strmerge.sh is failing in sparc targets.  This is
because it does an `elflint -d' in a debuginfo file, and this fails
with:

  section [21] '.plt' is both executable and writable

elflint uses the ebl_check_special_section hook (implemented only by
the alpha and sparc backends) in order to determine whether an
executable+writable section must be flagged or not.  In both cases the
hook will fail analyzing eu-strip debuginfo files (as they should,
because debuginfo files are broken ;).

This patch just modifies elflint to not use the hook when -d is
specified in the command-line.  This fixes the test in sparc-* and
sparc64-* targets (and presumably in alpha* targets too).

Additionaly, the patch checks that the type of WE sections in
debuginfo files is NOBITS.

Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com>