PowerVR SGX Acceleration

TI publishes [1] binary blobs for GPU support on their SoC with PowerVR SGX graphics. Unfortunately, these are built against GLIBC and only include wayland support.

Fortunately, there are also patches for Chromium [2] https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/media-libs/arc-mesa-img/files that include the DRI driver under the MIT license. The OpenGL and initialization libraries are still closed source, but fortunately they can be loaded the dlsym and work properly under musl.

This MR has two new aports - one for the PVR fork of Mesa, the other providing the SGX blobs that are required. The SGX blobs are broken down into subpackages for each SoC as they conflict with each other due to using the same filenames for each.

These are known to work with wlroots-based compositors (when there's a patch for the unpack subimage extension included) as well as Plasma mobile. X-based DEs do not currently work due to some bugs around OpenGL ES2 support in glamor/modesetting.

Related issues #932 (closed) #262 (closed)

[1] https://git.ti.com/cgit/graphics/omap5-sgx-ddk-um-linux [2] https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/master/media-libs/arc-mesa-img/files