Add SCons variant_dir support

[Ivorforce]

Supersedes #1439 - it's basically just a rebase. It compiles, but I haven't checked if it does what it says it does (allow godot-cpp to be included from elsewhere).

[Ivorforce]

Commenting "my own" PR because so far I've only rebased. Would like to see if anybody has comments on my comments, otherwise I'll probably just adjust things as I see fet.

[Ivorforce]

Alright, code wise, I think this is ready now.
I still haven't tested it though. Someone should probably do that before a merge (i may, but it may take a few more days).

[Ivorforce]

Alright, I tested this, it seems to work.

To use it, one has to call SConscript like env = SConscript("../SConstruct", variant_dir="build_folder"). I tested this from the test project.

[dsnopek]

To use it, one has to call SConscript like env = SConscript("../SConstruct", variant_dir="build_folder"). I tested this from the test project.

I tested this in the same way and it worked for me!

However, shouldn't this be an option given on the command-line, rather than something that developers hard-code into their project? Why not add this to other default options?

Also, this only seemed to affect the build artifacts from godot-cpp itself, and not the test project. What do developers need to do so that their artifacts also build in a separate directory?

[Ivorforce]

However, shouldn't this be an option given on the command-line, rather than something that developers hard-code into their project? Why not add this to other default options?
Also, this only seemed to affect the build artifacts from godot-cpp itself, and not the test project. What do developers need to do so that their artifacts also build in a separate directory?

This would be possible! I tested this as well, and arrived at this solution:

• Add a variant_dir command line option
• Call the VariantDir function with the appropriate value, if passed
• Compile <variant_dir>/* instead of src/* in godotcpp.py (or analogously, the user SConstruct)

As you observed, applying variant_dir godot-cpp side would only move godot-cpp object files, so the option would need to be added on the user side (godot-cpp-template?).