Add toolstate checking into bootstrap

This is not yet actually used by CI, but implements the logic for
checking that tools are properly building on beta/stable and during beta
cutoff week.

This attempts to mirror the checking functionality in
src/ci/docker/x86_64-gnu-tools/checktools.sh, and called scripts. It
does not attempt to run the relevant steps (that functionality was
originally desired to be moved into bootstrap as well, but doing so
proved more difficult than expected).

This is intended as a way to centralize and make clearer the logic
involved in toolstate checking. In particular, the previous logic was
spread across numerous python and shell scripts in such a way that made
interpretation quite difficult.

src/bootstrap/lib.rs

@@ -169,7 +169,6 @@ mod job {
 pub use crate::config::Config;
 use crate::flags::Subcommand;
 use crate::cache::{Interned, INTERNER};
-use crate::toolstate::ToolState;
 
 const LLVM_TOOLS: &[&str] = &[
     "llvm-nm", // used to inspect binaries; it shows symbol names, their sizes and visibility
@@ -1074,32 +1073,6 @@ impl Build {
         }
     }
 
-    /// Updates the actual toolstate of a tool.
-    ///
-    /// The toolstates are saved to the file specified by the key
-    /// `rust.save-toolstates` in `config.toml`. If unspecified, nothing will be
-    /// done. The file is updated immediately after this function completes.
-    pub fn save_toolstate(&self, tool: &str, state: ToolState) {
-        if let Some(ref path) = self.config.save_toolstates {
-            if let Some(parent) = path.parent() {
-                // Ensure the parent directory always exists
-                t!(std::fs::create_dir_all(parent));
-            }
-            let mut file = t!(fs::OpenOptions::new()
-                .create(true)
-                .read(true)
-                .write(true)
-                .open(path));
-
-            let mut current_toolstates: HashMap<Box<str>, ToolState> =
-                serde_json::from_reader(&mut file).unwrap_or_default();
-            current_toolstates.insert(tool.into(), state);
-            t!(file.seek(SeekFrom::Start(0)));
-            t!(file.set_len(0));
-            t!(serde_json::to_writer(file, &current_toolstates));
-        }
-    }
-
     fn in_tree_crates(&self, root: &str) -> Vec<&Crate> {
         let mut ret = Vec::new();
         let mut list = vec![INTERNER.intern_str(root)];