Auto merge of #38809 - alexcrichton:rustbuild-fresh, r=brson

rustbuild: Fix a few rebuilding issues

Did a bit of investigation and found a few small unrelated issues, but this should help clean up a lot of errors we've been seeing locally.

Author: bors

src/bootstrap/compile.rs

@@ -258,11 +258,6 @@ fn compiler_file(compiler: &Path, file: &str) -> PathBuf {
 }
 
 pub fn create_sysroot(build: &Build, compiler: &Compiler) {
-    // nothing to do in stage0
-    if compiler.stage == 0 {
-        return
-    }
-
     let sysroot = build.sysroot(compiler);
     let _ = fs::remove_dir_all(&sysroot);
     t!(fs::create_dir_all(&sysroot));
@@ -396,7 +391,7 @@ pub fn tool(build: &Build, stage: u32, host: &str, tool: &str) {
 /// all files in a directory and updating the stamp if any are newer.
 fn update_mtime(path: &Path) {
     let mut max = None;
-    if let Ok(entries) = path.parent().unwrap().read_dir() {
+    if let Ok(entries) = path.parent().unwrap().join("deps").read_dir() {
         for entry in entries.map(|e| t!(e)) {
             if t!(entry.file_type()).is_file() {
                 let meta = t!(entry.metadata());