LUA_CPATH_DEFAULT broken when not building with debhelper

There was an upstream changeset (5.1.4-6) which introduced DEB_HOST_MULTIARCH for the LUA_CPATH_DEFAULT like in luaconf.h, like so:
#define LUA_CDIR2 LUA_ROOT2 "lib/" DEB_HOST_MULTIARCH "/lua/5.1/"
...
#define LUA_CPATH_DEFAULT \
        "./?.so;" LUA_CDIR"?.so;" LUA_CDIR2"?.so;" LUA_CDIR3"?.so;" LUA_CDIR"loadall.so"
#endif

The DEB_HOST_MULTIARCH is only set during the Debian build process, or manually through the preprocessor. Since Lua packages are built in this way they include the LUA_CPATH_DEFAULT properly.

However, this change breaks the compilation of programs which embed Lua and rely upon LUA_CPATH_DEFAULT:
error: expected ')' before 'DEB_HOST_MULTIARCH'

A workaround is to set DEB_HOST_MULTIARCH manually (dpkg-architecture -qDEB_HOST_MULTIARCH), or construct ones own LUA_CPATH_DEFAULT.

This is a change between Oneiric (using 5.1.4-5) and Precise (5.1.4-12ubuntu1). Perhaps the affected population is small since this change has been in Debian since July 2011.