newapkbuild: use 'plain' buildtype for meson and 'None' buildtype for CMake
This way Meson and CMake will only use the C{,PP,XX}FLAGS we've set and not add additional flags (e.g. -O2/O3)
This way Meson and CMake will only use the C{,PP,XX}FLAGS we've set and not add additional flags (e.g. -O2/O3)