luajit adds source to kwargs breaking linking with Rust

[bobbens]

The LuaJIT wrap adds the luajit_h target as a source, thus adding the file luajit.h when specifying luajit as a dependency. This is usually not a problem for C/C++, but when linking to Rust, this will cause the compilation to fail with "ERROR: Rust target FOO contains a non-rust source file.". The offending code is:

luajit_dep_kwargs = {
  'include_directories': include_directories('.'),
  'sources'            : luajit_h,
  'variables'          : {
    'INSTALL_CMOD'     : install_cmod,
    'INSTALL_LMOD'     : install_lmod,
  },
}

My code only hits the issue with the fallback, it works fine with the system library.