[gtkada] Patch: Repair the support for directory variables.

[Emmanuel Briot]

>>    Exampledir := external("EXAMPLEDIR",
>> "share/examples/gtkada/testgtk"); for artifacts (Exampledir) use
>> (....)
>> 
> 
> Of course i tried the obvious. It made the project file syntactically
> invalid. GPRbuild requires a string literal, and so does the BNF in the
> GPRbuild User's Guide. Well it was GPRbuild 2015 that I tried it with,
> but the GPRbuild and GPR Companion Tools User’s Guide 2016 still
> requires a literal.

Which part requires a literal string in my example ? (I agree that there are
a number of cases in which gpr files must have literal strings, and sometimes
even for good reasons :-)
But in my example, I am using a literal string for the default value of "external",

Would you share (if you still have it) the experiment you performed ?

> As long as that's the case I don't find Artifacts to be of much use for
> a portable project. A cp command in the makefile works better.

True if you are only aiming at linux.
Not so if you want to support multiple systems.

Thanks !
Emmanuel