package/mesa3d: select gbm if no glx, no egl and no osmesa-classic

package/mesa3d: select gbm if no glx, no egl and no osmesa-classic

This issue has been trigged since [1]:
"package/mesa3d: add option to configure gbm support"

Before the patch, the gbm support was autodetected by meson and enabled
only when at least one dri driver was enabled [2].

On the Buildroot side, the gbm support was explicitely enabled only when
BR2_PACKAGE_MESA3D_OPENGL_EGL was set.

Now, the gbm support is explicitely disabled but the meson build system
check if at least one option OpenGL GLX or OpenGL EGL or GBM or
OSMesa (classic) library is enabled [3].

The previous behavious was to enable GBM when GLX, EGL and OSMesa are
disabled. So select GBM symbol for this case.

Fixes:
http://autobuild.buildroot.net/results/a14f329560f8022f7ba8ec43ad8eed84e005d226

[1] b6c051acf787c804e732bc58ba8d7e440701a168
[2] https://gitlab.freedesktop.org/mesa/mesa/blob/19.3/meson.build#L348
[3] https://gitlab.freedesktop.org/mesa/mesa/blob/19.3/meson.build#L449

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Tested-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>