Do not use relative includes for generated headers.

[jpakkane]

This commit changed the way includes are done. This causes a problem with generated headers because the include directives now look like this;

#include "../logo_svg.gen.h"

This forces the header to be relative to this source file, i.e. it has to be inside the source directory. This works fine with SCons because it does in-tree builds and writes the .gen.h files inside the source tree. This causes problems for the Meson port, which writes all generated files in a separate build directory so this include directive can not really work.

This patch restores the old behaviour that works with both systems but only for files that are generated during the build.

[jpakkane]

The issue reported by CI should be fixed now, but this requires a reapproval so the test suite is run again.

[fire]

@akien-mga Looks good? But I don't understand how we got here.

[aaronfranke]

Makes sense to me, and the code looks correct.

[akien-mga]

I'm not fond of reverting that change, as it goes against the goal of making platform ports self-contained and modular, enabling easy plug 'n compile behavior for new / thirdparty platform ports.

We have other places with relative include paths for .gen.h files, why do those work but not the platform ones?

scene/resources/default_theme/default_theme.cpp
34:#include "default_font.gen.h"
35:#include "default_theme_icons.gen.h"

modules/lightmapper_rd/lightmapper_rd.cpp
33:#include "lm_blendseams.glsl.gen.h"
34:#include "lm_compute.glsl.gen.h"
35:#include "lm_raster.glsl.gen.h"

modules/text_server_adv/text_server_adv.cpp
63:#include "icudata.gen.h"

editor/editor_fonts.cpp
33:#include "builtin_fonts.gen.h"

editor/editor_help.cpp
38:#include "doc_data_compressed.gen.h"

If it's only the ../ part that Meson can't handle, then I would suggest changing the code that generates logo_svg.gen.h and run_icon_svg.gen.h so that those get generated in the platform/*/export/ folders instead of platform/*/, since that's the only place where they're used.

[akien-mga]

If it's only the ../ part that Meson can't handle, then I would suggest changing the code that generates logo_svg.gen.h and run_icon_svg.gen.h so that those get generated in the platform/*/export/ folders instead of platform/*/, since that's the only place where they're used.

Done with #78435, let me know if that solves the issue for the Meson port.

[akien-mga]

Should be superseded by #78435, but let me know if that's not sufficient and we can rediscuss further changes.