Improve flexibility around vendored librariesmain

compat53 is vendored since #1757 as it is required to run luarocks with lua 5.1 or 5.2.

However, this introduced some issues as the GNUmakefile install rule places these in the same place where `luarocks install compat53` would install them. This means you get conflicts if you install the actual package:
```
Warning: /.../prefix/share/lua/5.1/compat53/init.lua is not tracked by this installation of LuaRocks. Moving it to /.../prefix/share/lua/5.1/compat53/init.lua~
Warning: /.../prefix/share/lua/5.1/compat53/module.lua is not tracked by this installation of LuaRocks. Moving it to /.../prefix/share/lua/5.1/compat53/module.lua~
Warning: /.../prefix/share/lua/5.1/compat53/file_mt.lua is not tracked by this installation of LuaRocks. Moving it to /.../prefix/share/lua/5.1/compat53/file_mt.lua~
```

It is also not ideal for linux package maintainers to include a vendored package, see: https://github.com/luarocks/luarocks/pull/1757#issuecomment-3409873412.

To solve these issues, this patchset makes the following changes:
- GNUmakefile now places the compat53 files under `luarocks/vendor/compat53` (which is added internally to the luarocks script's `package.path`). This way a user's installation of compat53 does not interfere at all with luarocks one.
- Added `--with-system-compat53` option to configure script for external packaging systems.
- Fixed install.bat's logic for deciding whether to vendor compat53, as the current script includes it for every version.

install.bat already places luarocks sources outside of LUAPATH, so that part can stay as is.

I've also inverted the version check to avoid the need for future patches like: #1850.

1 files changed, 7 insertions, 0 deletions

diff --git a/configure b/configure
index 170f4ede..7253dc61 100755
--- a/configure
+++ b/configure
@@ -143,6 +143,9 @@ For specialized uses of LuaRocks:
                                (e.g. when only deploying binary packages)
                                you do not need lua.h installed. This flag
                                skips the check for lua.h in "configure".
+  --with-system-rocks          Use an external installation of rocks required
+                               for running luarocks instead instead of the
+                               vendored versions.
 
 EOF
 }
@@ -301,6 +304,9 @@ do
    --disable-incdir-check)
       DISABLE_INCDIR_CHECK=yes
       ;;
+   --with-system-rocks)
+      WITH_SYSTEM_ROCKS=yes
+      ;;
 
    # Old options that no longer apply
    # --------------------------------
@@ -500,6 +506,7 @@ LUA_BINDIR=$LUA_BINDIR
 LUA_INCDIR=$LUA_INCDIR
 LUA_LIBDIR=$LUA_LIBDIR
 FORCE_CONFIG=$FORCE_CONFIG
+WITH_SYSTEM_ROCKS=$WITH_SYSTEM_ROCKS
 EOF
 
 echo