mc: wire recipe into build tree, fix gnulib mountlist detection

- Create recipes/tui/mc symlink to local/recipes/tui/mc
- Remove conflicting WIP recipes/wip/files/mc shadow
- Add sed fix for mountlist.m4 AC_MSG_ERROR -> AC_MSG_WARN
  because Redox has no /etc/mtab or /proc/mounts
- mc still needs more work: configure succeeds but make
  regeneration of configure from m4 files undoes the fix

local/recipes/tui/mc/recipe.toml

@@ -43,5 +43,10 @@ COOKBOOK_CONFIGURE_FLAGS+=(
     --with-screen=ncurses
 )
 
+# Fix gnulib mountlist detection: Redox has no /etc/mtab or /proc/mounts.
+# Change the configure error to a warning so the build proceeds.
+sed -i 's/AC_MSG_ERROR(\[could not determine how to read list of mounted file systems\])/AC_MSG_WARN([could not determine how to read list of mounted file systems]); ac_list_mounted_fs=missing/' \
+    "${COOKBOOK_SOURCE}/m4.include/gnulib/mountlist.m4"
+
 cookbook_configure
 """