Skip target sanity check for local rebuilds

Author: bjorn3

src/bootstrap/src/core/sanity.rs

@@ -96,6 +96,10 @@ pub fn check(build: &mut Build) {
         path.components().any(|component| skipped_paths.contains(&component.as_os_str()))
     });
 
+    // Skip target sanity checks when doing a local rebuild as in that case stage0
+    // likely knows about our new targets.
+    skip_target_sanity |= build.config.local_rebuild;
+
     let path = env::var_os("PATH").unwrap_or_default();
     // On Windows, quotes are invalid characters for filename paths, and if
     // one is present as part of the PATH then that can lead to the system