ada: Fix ALI elaboration flags for ghost compilation units

ada: Fix ALI elaboration flags for ghost compilation units

When GNAT was compiling a ghost unit, the ALI file wrongly suggested that this
unit includes elaboration code, which caused linking errors to non-existing
elaboration counters. This was because elaboration code is only detected in
Gigi, which is skipped for ignored ghost units, because we don't generate
object code for them

gcc/ada/ChangeLog:

	* gnat1drv.adb (Gnat1drv): Do minimal decoration of the spec and body
	of an ignored ghost compilation unit.