Extract upstream libarchive using the following shell code.

url=git://github.com/libarchive/libarchive.git &&
v=3.1.2 &&
r=19f23e19 &&
paths="
  CMakeLists.txt
  COPYING
  CTestConfig.cmake
  build/cmake
  build/pkgconfig
  build/utils
  build/version
  libarchive/*.*
" &&
mkdir libarchive-$v-g$r-reduced &&
git clone $url libarchive-git &&
date=$(cd libarchive-git && git log -n 1 --format='%cd' $r) &&
(cd libarchive-git && git archive --format=tar $r -- $paths) |
(cd libarchive-$v-g$r-reduced && tar xv) &&
fromdos libarchive-$v-g$r-reduced/build/cmake/Find*.cmake &&
echo "g$r date: $date"