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 <[email protected]>
Reported-By: Andres Freund <[email protected]>
Reported-By: Thomas Munro <[email protected]>
Author: Andres Freund <[email protected]>
Discussion: https://postgr.es/m/20201201064949[email protected]
Backpatch: 11-, where jit support was added