www/node,www/node8,www/node6: disable dtrace usdt on armv[67]

Disable the DTRACE option by default on armv[67] since Node.js fails to
build on armv[67] with the following error:

dt_modtext:/usr/src/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c(820): arm not implemented

PR: 224271
Submitted by: mikael.urankar@gmail.com