ada: Small fix in expansion of array aggregates handled by the back end

ada: Small fix in expansion of array aggregates handled by the back end

The (minimal) expansion is now done by Build_Array_Aggr_Code in all cases,
which means that it must prevent the aggregate from being re-analyzed as
the RHS of the assignment, which may trigger a bogus warning and lead to
another useless rewriting.

The change also inlines Build_Assignment_With_Temporary that is now called
only once by Build_Array_Aggr_Code for this processing.

gcc/ada/ChangeLog:

	* exp_aggr.adb (Build_Assignment_With_Temporary): Inline into...
	(Build_Array_Aggr_Code): ...this.  Set the Analyzed flag on the
	relocated aggregate if it is to be handled by the back-end.