* Switch mesa support from DRI to gallium
Supported drivers are
- softpipe (Sebstian Sumpf)
- iris for Intel GPUs (Alexander Boetcher)
- etnaviv for Vivante GPUs (Josef Söntgen)
* Mesa's generated files are placed into 'contrib/mesa-<hash>/generated'
and are cloned per default from a separate Git repo in order to avoid
hash updates upon package build. In case you need to generate files
yourself use
! prepare_port mesa GENERATE_FILES=1
issue #4254
Support for iris and etnvaviv
* entaviv:
- libdrm on FreeBSD is not prepared for !PCI (and libc our is missing
<sys/pciio.h>
- missing <sys/types.h> include in xf86drmMode.c
- etnaviv relies on linux header files - dummy in $(INC_DIR)
- IOCTL FreeBSD ↔ Linux have swapped IO/OUT bit
- O_CLOEXEC differs between FreeBSD ↔ Linux
issue #4254
