pgsql: Fix GiST buffering build to work when there are included columns

Fix GiST buffering build to work when there are included columns.

gistRelocateBuildBuffersOnSplit did not get the memo about which
attribute count to use.  This could lead to a crash if there were
included columns and buffering build was chosen.  (Because there
are random page-split decisions elsewhere in GiST index build,
the crashes are not entirely deterministic.)

Back-patch to v12 where GiST gained support for included columns.

Pavel Borisov

Discussion: https://postgr.es/m/CALT9ZEECCV5m7wvxg46PC-7x-EybUmnpupBGhSFMoAAay+r6HQ@mail.gmail.com

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/962ab473ec3d4c1090ba75fa677167126956c1ee

Modified Files
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src/backend/access/gist/gistbuildbuffers.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)