pgsql: jit: configure: Explicitly reference 'native' component.

jit: configure: Explicitly reference 'native' component.

Until recently 'native' was implicitly included via 'orcjit', but a change
included in LLVM 11 (not yet released) removed a number of such indirect
component references.

Reported-By: Fabien COELHO <coelho@cri.ensmp.fr>
Reported-By: Andres Freund <andres@anarazel.de>
Reported-By: Thomas Munro <thomas.munro@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20201201064949.mex6kvi2kygby3ni@alap3.anarazel.de
Backpatch: 11-, where jit support was added

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/9543f0861b1d9b566be88edae21f24fb1377f45c

Modified Files
--------------
config/llvm.m4 | 1 +
configure      | 1 +
2 files changed, 2 insertions(+)