Rollup merge of #36663 - brson:build-plan, r=alexcrichton

rustbuild: Print out all build steps when --verbose

These helped me debug some problems with the asmjs target. It's just vomiting debug representations, so not the prettiest stuff.

r? @alexcrichton

src/bootstrap/lib.rs

@@ -243,7 +243,14 @@ impl Build {
         // Almost all of these are simple one-liners that shell out to the
         // corresponding functionality in the extra modules, where more
         // documentation can be found.
-        for target in step::all(self) {
+        let steps = step::all(self);
+
+        self.verbose("bootstrap build plan:");
+        for step in &steps {
+            self.verbose(&format!("{:?}", step));
+        }
+
+        for target in steps {
             let doc_out = self.out.join(&target.target).join("doc");
             match target.src {
                 Llvm { _dummy } => {

src/bootstrap/step.rs

@@ -171,6 +171,8 @@ targets!(define_source);
 /// into a topologically sorted list which when executed left-to-right will
 /// correctly sequence the entire build.
 pub fn all(build: &Build) -> Vec<Step> {
+    build.verbose("inferred build steps:");
+
     let mut ret = Vec::new();
     let mut all = HashSet::new();
     for target in top_level(build) {
@@ -184,6 +186,7 @@ pub fn all(build: &Build) -> Vec<Step> {
                 set: &mut HashSet<Step<'a>>) {
         if set.insert(target.clone()) {
             for dep in target.deps(build) {
+                build.verbose(&format!("{:?}\n  -> {:?}", target, dep));
                 fill(build, &dep, ret, set);
             }
             ret.push(target.clone());