nfs-utils: Enable unknown-warnings as errors
nfs-utils: Enable unknown-warnings as errors

This helps configure scripts to detect right set of
compiler specific options to enable

Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

kraj/meta-clang,kraj/meta-clang,kraj/meta-clang