pgsql: LLVMJIT: Release JIT context after running ExprContextshutdown

LLVMJIT: Release JIT context after running ExprContext shutdown callbacks.

Due to inlining it previously was possible that an ExprContext's
shutdown callback pointed to a JITed function. As the JIT context
previously was shut down before the shutdown callbacks were called,
that could lead to segfaults.  Fix the ordering.

Reported-By: Dmitry Dolgov
Author: Andres Freund
Discussion: https://postgr.es/m/CA+q6zcWO7CeAJtHBxgcHn_hj+PenM=tvG0RJ93X1uEJ86+76Ug@mail.gmail.com
Backpatch: 11-, where JIT compilation was added

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/ed7e319eb41361250ccb19379ef206b4a6d866de

Modified Files
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src/backend/executor/execMain.c  |  5 -----
src/backend/executor/execUtils.c | 18 +++++++++++++-----
2 files changed, 13 insertions(+), 10 deletions(-)