weston/1.0.6-r0/weston-1.0.6$ grep -R unwind configure.ac
PKG_CHECK_MODULES(LIBUNWIND, libunwind,
                  [have_libunwind=yes], [have_libunwind=no])
if test "x$have_libunwind" = xyes; then
       AC_DEFINE(HAVE_LIBUNWIND, 1, [Have libunwind support])
AM_CONDITIONAL(HAVE_LIBUNWIND, [test "x$have_libunwind" = xyes])