main/mesa: consolidate subpackages

Mesa uses so-called "megadrivers" to link multiple drivers into
one shared library. Essentially there are only 4 distinct shared
libraries built:

   - libmesa_dri_drivers.so ("classic" DRI drivers)
   - libgallium_dri.so (Gallium DRI drivers)
   - libgallium_drv_video.so (Gallium VAAPI drivers)
   - libvdpau_gallium.so.1.0.0 (Gallium VDPAU drivers)
   - (Note: Vulkan drivers are all built separately)

These shared libraries are then hard-linked for each driver
(i965, radeon, freedreno, ...).

The APKBUILD attempts to create minimal packages by splitting
the drivers into separate subpackages.
Unfortunately this has exactly the opposite effect in this case.

Instead of preserving the hard links with one large Mesa package,
we copy the same shared library over and over again into separate
subpackages. This causes significant overhead for storing all the
apk packages, but also when installing multiple drivers on one system.

The only useful separation we can make are the megadrivers themselves,
i.e. one subpackage for each of the shared libraries mentioned above.
7 jobs for !2816 with mesa-megadrivers in 11 minutes and 53 seconds (queued for 1 second)
latest detached
Status Job ID Name Coverage
  Lint
failed #34293
x86_64 docker-alpine allowed to fail
lint

00:00:30

 
  Build
passed #34298
aarch64 ci-build docker-alpine
build-aarch64

00:05:24

passed #34299
armv7 ci-build docker-alpine
build-armv7

00:05:41

passed #34297
ppc64le ci-build docker-alpine
build-ppc64le

00:06:09

passed #34296
s390x ci-build docker-alpine
build-s390x

00:02:44

passed #34295
x86 ci-build docker-alpine
build-x86

00:06:17

passed #34294
x86_64 ci-build docker-alpine
build-x86_64

00:05:38

 
Name Stage Failure
failed
lint Lint
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