[yocto] Error do_compile libepoxy

[Alexander Kanavin]

> I'll try to recap a little bit but, please, forgive my ignorance in
> graphics stacks and libraries.
> Disclaimer: mostly working on headless systems... my bad!
> This is what I think I understand here (remember I test building poky
> + meta-raspberrypi):
> * libepoxy recipe in poky uses PACKAGECONFIG to conditionally depend
> on virtual/X11 when this is available in DISTRO_FEATURE
> * the latter is the case for poky which is the DISTRO I'm building
> for. This gives i.e. a populated recipe-sysroot/usr/include/X11
> * upstream meson.build conditionally builds tests if X11 is
> available... so we expect they should build fine in this case
> * compile fails on test/egl_common.c which does not explicitly include
> X11/Xlib.h by itself. Doing so moves things forward but, to me, does
> not seem to be the right thing to do.
> 
> Is this correct to assume that the upstream tested usecases are
> probably getting the include otherwise, maybe conditionally as Alex
> initially suggested. If so, where should we look for the missing
> pieces?

I'm similarly ignorant about this stuff (our resident graphics stack 
expert Jussi Kukkonen left a few months ago), but let's consider the 
build files:

- the offending tests are wrapped in "if build_egl and build_x11_tests"

- build_egl is controlled by a PACKAGECONFIG, and I guess you do have it 
available

- "build_x11_tests = build_glx and x11_dep.found()" - build_glx is 
similarly controlled by a PACKAGECONFIG, and enabled if x11 is in 
DISTRO_FEATURES:

PACKAGECONFIG[x11] = "-Denable-glx=yes, -Denable-glx=no, virtual/libx11"
PACKAGECONFIG ??= "${@bb.utils.filter('DISTRO_FEATURES', 'x11', d)} egl"

This is where I think the configuration is not quite right. Instead of 
virtual/libx11, it should say virtual/libgl. And if that dependency 
cannot be satisfied, then the x11 option should be altogether disabled 
in the distro/local config (in poky mesa provides virtual/libgl). At 
least that's how it's configured in many other recipes throughout oe-core.

Can you try:
a) disabling x11 PACKAGECONFIG in your local config and see if things build?
b) changing the dependency in that option to virtual/libgl and see what 
kind of error you get, if any. I guess this is the right fix after all.

Alex