By default, the executable file name corresponding to a main source is
deduced from the main source file name. Through the attributes
Executable_Suffix of package
it is possible to change this default.
Debug above, the executable file name
for main source proc.adb is
Executable_Suffix, when specified, may change the suffix
of the executable files, when no attribute
its value replace the platform-specific executable suffix.
Executable_Suffix are the only ways to
specify a non-default executable file name when several mains are built at once
in a single gnatmake command.