Introduce luarocks hardcoded config for static build

Currently, we use the same luarocks hardcoded config for static build as
for regular build. As a result, LUA_BINDIR, LUA_INCDIR, SYSCONFDIR, and
PREFIX point to locations inside the build directory, which doesn't make
any sense.

Let's introduce a special hardcoded config which will set those
directories to locations relative to the binary location:

 - LUA_BINDIR: directory where the binary is located (bindir)
 - PREFIX: <dir> if bindir is <dir>/bin, otherwise bindir.
 - LUA_INCDIR: PREFIX/include/tarantool
 - SYSCONFDIR: PREFIX/etc/tarantool/rocks

Also, let's add the PREFIX/rocks to the rocks path if present.

This is needed for Tarantool SDK bundle to work as expected.
In particular the check for <dir>/bin is needed, because SDK
installs binaries in bundle root, not in /bin.