Log Message:
devel/boost-libs: Handle stacktrace.addr2line in cross-builds.

This is a stop-gap measure because I don't know how to spell, e.g.,

CONFIGURE_ARGS+=	ac_cv_addr2line_path=/usr/bin/addr2line

in boost-jamlish.

No change to native builds, and cross builds were broken without this
change, so no revbump.