sh: avoid warnings about too-long initializer stringsHEADmain

Mark `optletter` and `t_op::op_text` as `__non_string`, to avoid
warnings from clang 21 similar to:

    bin/sh/options.h:77:36: error: initializer-string for character array is too long, array size is 19 but initializer has size 20 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Werror,-Wunterminated-string-initialization]
       77 | const char optletter[NSHORTOPTS] = "efIimnsxvVECabupTPh";
          |                                    ^~~~~~~~~~~~~~~~~~~~~
    bin/test/test.c:153:3: error: initializer-string for character array is too long, array size is 2 but initializer has size 3 (including the null terminating character); did you mean to use the 'nonstring' attribute? [-Werror,-Wunterminated-string-initialization]
      153 |         {"==",  STREQ},
          |          ^~~~

MFC after:	3 days
Reviewed by:	jilles
Differential Revision: https://reviews.freebsd.org/D54362

0 files changed, 0 insertions, 0 deletions