cc: detect -lunwind for C (already automatic for C++) and build libun…

…wind when needed

only verify .done files in test-build-sysroot-race.sh when testing a …

…dev build

include libDER in macos sysroots (macos >=11)

lib.sh: make sure OUT_DIR exists in _regenerate_sysinc_dir

etc/dist.sh: put archive in out/ dir instead of out/compis-v... dir

bump version

lots of little improvements

add examples/arrays-and-slices.co