Refactor dtrace postprocessing make rules
This is in preparation for building postgres with meson / ninja.
Move the dtrace postprocessing sed commands into a separate file so
that it can be shared by meson. Also split the rule into two for
proper dependency declaration.
Reviewed-by: Andres Freund <andres@anarazel.de>
Author: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/
5e216522-ba3c-f0e6-7f97-
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