Auto merge of #35340 - michaelwoerister:incr-comp-cli-args, r=nikomat…

…sakis

Take commandline arguments into account for incr. comp.

Implements the conservative strategy described in rust-lang/rust#33727.

From now one, every time a new commandline option is added, one has to specify if it influences the incremental compilation cache. I've tried to implement this as automatic as possible: One just has to added either the `[TRACKED]` or the `[UNTRACKED]` marker next to the field. The `Options`, `CodegenOptions`, and `DebuggingOptions` definitions in `session::config` show plenty of examples.

The PR removes some cruft from `session::config::Options`, mostly unnecessary copies of flags also present in `DebuggingOptions` or `CodeGenOptions` in the same struct.

One notable removal is the `cfg` field that contained the values passed via `--cfg` commandline arguments. I chose to remove it because (1) its content is only a subset of what later is stored in `hir::Crate::config` and it's pretty likely that reading the cfgs from `Options` would not be what you wanted, and (2) we could not incorporate it into the dep-tracking hash of the `Options` struct because of how the test framework works, leaving us with a piece of untracked but vital data.

It is now recommended (just as before) to access the crate config via the `krate()` method in the HIR map.

Because the `cfg` field is not present in the `Options` struct any more, some methods in the `CompilerCalls` trait now take the crate config as an explicit parameter -- which might constitute a breaking change for plugin authors.

src/runtest.rs

@@ -2008,6 +2008,7 @@ actual:\n\
         // Add an extra flag pointing at the incremental directory.
         let mut revision_props = self.props.clone();
         revision_props.incremental_dir = Some(incremental_dir);
+        revision_props.compile_flags.push(String::from("-Zincremental-info"));
 
         let revision_cx = TestCx {
             config: self.config,