message: Change println macro to drop_println
  I figured out the error was me improperly using the macro. CI build
  failed because `println` macro is not allowed in Cargo codebase.
diff: @@ -27,6 +27,7 @@ use std::hash::{Hash, Hasher};
  use std::io::Write;
  use std::sync::Arc;
  +use crate::drop_println;
  use crate::core::compiler::standard_lib;
  use crate::core::compiler::unit_dependencies::build_unit_dependencies;
  use crate::core::compiler::unit_graph::{self, UnitDep, UnitGraph};
  @@ -306,7 +307,7 @@ pub fn print<'a>(
  let rustc = config.load_global_rustc(Some(ws))?;
  for (index, kind) in build_config.requested_kinds.iter().enumerate() {
  if index != 0 {
  - println!();
  + drop_println!(config);
  }
  let rustflags = env_args(
  config,
  