Fix -DBUILD_WITH_STRICT_TMPPATH dtrace builds

Some of the scripts used for libdtrace invoke nawk instead of awk
(for example cddl/contrib/opensolaris/lib/libdtrace/common/mknames.sh).
When bootstrapping all tools, we get the nawk -> awk link while building
usr.bin/awk, but when linking/copying the dependencies from the host we
were only adding awk but not nawk.

This was silently generating invalid files when building libdtrace with
BUILD_WITH_STRICT_TMPPATH=1 since those scripts invoke nawk instead of
awk. In addition to adding the missing link this commit also adds
set -e to those scripts to catch errors like this in the future.

Reviewed By: markj, emaste
Differential Revision: https://reviews.freebsd.org/D26025