Function build_serde_json_value

pub(crate) fn build_serde_json_value(drv: Derivation) -> Value

construct a serde_json::Value from a Derivation. Some environment values can be non-valid UTF-8 strings. serde_json prints them out really unreadable. This is a tool to print A-Terms in a more readable fashion, so we brutally use the std::string::ToString implementation of bstr::BString to get a UTF-8 string (replacing invalid characters with the Unicode replacement codepoint).