Fix build on NetBSD: Walkaround compiler strictness regarding const conversion

Fix build on NetBSD: Walkaround compiler strictness regarding const conversion

This commit walks-around over-cautious Clang/LLVM alerts like:

/tmp/pkgsrc-tmp/wip/coreclr-git/work/coreclr/src/pal/tests/palsuite/c_runtime/sscanf/test4/test4.c:32:33: error: implicit conversion from
                'int' to 'short' changes value from 65535 to -1 [-Werror,-Wconstant-conversion]
 DoShortNumTest("-1", "%hd", 65535);
                ^~~~~~~~~~~~~~~~~~~

This closes #2968 "implicit conversion from 'int' to 'short' changes value from 65535 to -1"

Thanks Jan Kotas (Microsoft) for pointers.