pgsql: Refactor dtrace postprocessing make rules

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-f0e6-7f97-5276d0270029@enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/eb6569fd0e24e2f0502ef7b496ba0d3125bd4f15

Modified Files
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src/backend/utils/Makefile               | 21 +++++++--------------
src/backend/utils/postprocess_dtrace.sed | 15 +++++++++++++++
2 files changed, 22 insertions(+), 14 deletions(-)