pgsql: Fix crash when ALTER TABLE recreates indexes on partitions

Fix crash when ALTER TABLE recreates indexes on partitions

The skip_build flag was not being passed correctly when recursing to
indexes on partitions, leading to attempts to rebuild indexes when they
were not yet ready to be rebuilt.

Reported-by: Rajkumar Raghuwanshi
Discussion: https://postgr.es/m/CAKcux6mxNCGsgATwf5CGMF8g4WSupCXicCVMeKUTuWbyxHOMsQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/41372071dfaab97a1a8dca83e32b88413460f477

Modified Files
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src/backend/commands/indexcmds.c       | 2 +-
src/test/regress/expected/indexing.out | 8 ++++++++
src/test/regress/sql/indexing.sql      | 9 +++++++++
3 files changed, 18 insertions(+), 1 deletion(-)