Update mesa to version 20.0.8 (bug #58689). * src/mesa.mk: Update version and checksum. Add build-meson to dependecies. Update build rule to use meson and ninja as the build tools. * src/mesa-1-meson.patch: Add new patch. * src/mesa-1-fixes.patch: Remove old patch for the scons rule that is no longer needed. * dist-files.mk: Update file list. * src/build-mako.mk: Depend on and use python3. * src/build-markupsafe.mk: Depend on and use python3.

^settings\.mk
^usr/
^log/
^pkg/
^built-packages/
^installed-packages/
^wip/
^tmp-.*/

^autom4te\.cache/
^configure
^config\.status
^config\.log
^Makefile
^cmake-toolchain-file\.stamp

^cross-tools/
^gnuplot/
^octave/
^tools/makeinst-script\.sh
^tools/set-mxe-env\.sh