lua*Packages.compat53: improve paths

Test case that should execute without an error:
echo "require('compat53')" | env NIX_PATH=nixpkgs=$(pwd) \
  nix-shell --pure -p lua -p lua.pkgs.compat53 --run lua

pkgs/top-level/lua-packages.nix

@@ -151,10 +151,11 @@ with self; {
       cc lutf8lib.c $CFLAGS -o utf8.so
     '';
 
-    # There's no need to separate *.lua and *.so, I guess?  TODO: conventions?
+    # The hook in ../development/lua-modules/generic/default.nix
+    # is strict about share vs. lib for _PATH and _CPATH.
     installPhase = ''
-      install -Dt "$out/lib/lua/${lua.luaversion}/compat53" \
-        compat53/*.lua *.so
+      install -Dt "$out/share/lua/${lua.luaversion}/compat53" compat53/*.lua
+      install -Dt "$out/lib/lua/${lua.luaversion}/compat53" *.so
     '';
 
     meta = with stdenv.lib; {