Fixes to "PR 31728 testcases"

Fixes to "PR 31728 testcases"

This brings us down to just these fails for the set of targets I
usually test when making testsuite changes.
aarch64-pe  +FAIL: ld-pe/symbols-ordinals-hints-imports-ld
arm-pe  +FAIL: ld-pe/symbols-ordinals-hints-exports-dlltool
arm-pe  +FAIL: ld-pe/symbols-ordinals-hints-imports-dlltool

The aarch64 one is likely due to the target missing support somewhere.
It is fairly new, I haven't investigated.  The arm-pe fails are due to
arm-pe being a target that adds underscores to symbol names (see
config.bfd) whereas dlltool thinks it does not (see
dlltool.c:asm_prefix).  arm-wince-pe on the other hand doesn't add
underscores.  I would guess the right fix for dlltool is to get this
symbol info from bfd using bfd_get_target_info.

Note I'm not very happy about the creative use of ld_after_inputfile
in symbols-ordinals-hints-imports-ld.d, which is likely to break with
some future run_dump_test change.