pgsql: meson: Fix installation path computation

meson: Fix installation path computation

We have the long-standing logic to append "postgresql" to some
installation paths if it does not already contain "pgsql" or
"postgres".  The existing meson implementation of that only considered
the subdirectory under the prefix, not the prefix itself.  Fix that,
so that it now works the same way as the implementation in
Makefile.global.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/a6a6de12-f705-2b33-2fd9-9743277deb08@enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/8f6858064b1442f9ad057d289b0e4f018a2ad8aa

Modified Files
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meson.build | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)