The object directory for a project is the directory containing the compiler's output (such as ALI files and object files) for the project's immediate sources.
The object directory is given by the value of the attribute Object_Dir
in the project file.
for Object_Dir use "objects";
The attribute Object_Dir has a string value, the path name of the object
directory. The path name may be absolute or relative to the directory of the
project file. This directory must already exist, and be readable and writable.
By default, when the attribute Object_Dir is not given an explicit value
or when its value is the empty string, the object directory is the same as the
directory containing the project file.