Using tangram-es as a library with platform-specific tweaks

[tehKaiN]

In the past, I've done the wxwidgets support by adding platforms/wxwidgets files on a separate branch in my fork. This solution was flawed, because it needed separate set of hacks when building on windows/linux/rpi-linux. So I thought that I could do as follows:

• create wxTangram repo
• tangram-es is a submodule of wxTangram
• when configuring cmake, the tangram-es auto-deduces windows/linux/rpi
• thus configured tangram lib is used by wxTangram as a base

And this is problematic because currently, the tangram-es' CMake exposes following targets:

• tangram-core - base library, without platform-dependent stuff (gl_platform ifdefs, urlclient)
• trangram - executable with platform-specific tweaks (cmake vars, defines which switch things on and off, platform-specific link libraries)

What I would like to propose is as follows:

• add intermediate step of libtangram, which would consist of tangram-core and platform specific tweaks (platform_gl, urlclient),
• add separate target of glfwApp which would use libtangram

but is this feasible for all the platforms (ios, android)?

[mathisloge]

I've needed this aswell and had a local fork of this with some more additions. I've added a example in #2280

[matteblair]

This seems like a useful idea. I'm going to move this into a discussion, I think that's more appropriate than an issue at this point.