Fix list join argument in avante#build function

[snowphone]

Changes:

• Correct the join function arguments to be a list by adding square brackets around them
• This ensures proper concatenation of strings from luaeval("require('avante_lib').load()") and luaeval("require('avante.api').build(_A)", l:source)

Note that even after this commit is merged, still #453 error exists.

[aarnphm]

550 should fix this