tests: xfail readelf phdr count test w/LLVM binutils

LLVM readelf does not (yet) support phdr counts that overflow 16 bits.
Temporarily xfail this test until fixed; see upstream issue 132216 for
more details https://github.com/llvm/llvm-project/issues/132216.

PR: 285547
Reported by: markj
Reviewed by: dim, markj
Sponsored by: The FreeBSD Foundation
Fixes: 1cae7121c667 ("Enable LLVM_BINUTILS by default")
Differential Revision: https://reviews.freebsd.org/D49561