pgsql: Add NO_INSTALL option to pgxs

Add NO_INSTALL option to pgxs

Apply in libpq_pipeline test makefile, so that the test file is not
installed into tmp_install.

Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/cb9d16a6-760f-cd44-28d6-b091d5fb6ca7%40enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6abc8c2596dbfcb24f9b4d954a1465b8015118c3

Modified Files
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doc/src/sgml/extend.sgml                 | 10 ++++++++++
src/makefiles/pgxs.mk                    | 13 +++++++++++++
src/test/modules/libpq_pipeline/Makefile |  2 ++
3 files changed, 25 insertions(+)