pgsql: Fix optimization hazard in gram.y's makeOrderedSetArgs(), redux.

Fix optimization hazard in gram.y's makeOrderedSetArgs(), redux.

It appears that commit cf63c641c, which intended to prevent
misoptimization of the result-building step in makeOrderedSetArgs,
didn't go far enough: buildfarm member hornet's version of xlc
is now optimizing back to the old, broken behavior in which
list_length(directargs) is fetched only after list_concat() has
changed that value. I'm not entirely convinced whether that's
an undeniable compiler bug or whether it can be justified by a
sufficiently aggressive interpretation of C sequence points.
So let's just change the code to make it harder to misinterpret.

Back-patch to all supported versions, just in case.

Discussion: https://postgr.es/m/1830491.1601944935@sss.pgh.pa.us

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/eb48619d01d77d8273f4effa64f7ad544db8bb35

Modified Files
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src/backend/parser/gram.y | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)