Stop using `touch_arg` in `touch`

In #40040 (closed) we added the touch option to rbm, from tor-browser-build/rbm.conf.

The rbm.conf version assumed that the argument was following on the same line, but the new version expects a touch_arg option. I think we should use the rbm.conf version since the touch_arg doesn't work well in some cases, for example:

projects/tor-browser/build:  find "$PKG_DIR" -exec [% c("touch") %] {} \;
projects/tor/build:find -type f -print0 | xargs -0 [% c("touch") %]