[PATCH] Add strings -n testcase

[pengxu@kylinos.cn]

Hi all,

This patch adds test cases for the strings -n option in binutils-all/strings.exp. The -n option is used to limit the length of displayed symbols, which is default 4.

Changes:
Added a new test in binutils/testsuite/binutils-all/strings.exp to verify that strings -n correctly filter the symbols.

Testing:
Built binutils from source  and ran:
  make check-binutils RUNTESTFLAGS="binutils-all/strings.exp"
All tests pass, including the newly added one.

check binutils.sum:
...
Running /root/binutils-gdb/binutils/testsuite/binutils-all/strings.exp ...
PASS: strings: decoding little-endian multibyte strings
PASS: strings -f prints filename prefix
PASS: strings default minimum length (4)
                                  ==== binutils Summary ====
# of expected passes                      3