deb: give the build-user setup and resume cleanup their own phases

The profile's build-dependency phase spanned everything between the
apt passes and the build step, and for a kernel incremental build
that hid ~13 minutes of housekeeping: the recursive chown handing
the staged tree to the build user, and the resume_clear quirk
dropping the previous attempt's stamp caches. Both now enter the
profiler (ClearingResumeCaches only when the quirk has paths and a
tree is carried, PreparingBuildUser only for rootless builds), so
the status bar and pkh deb profile show where the time actually
goes — on a large carried tree the chown dominates, which is the
honest answer to a 6m30s DEPS column next to a 19m19s phase.

src/deb/mod.rs

@@ -43,6 +43,12 @@ pub enum Phase {
     InjectingPackages,
     /// apt-get build-dep
     InstallingBuildDeps,
+    /// Drop the resumed tree's input-untracked stamp caches (quirk:
+    /// `resume_clear`)
+    ClearingResumeCaches,
+    /// Create the unprivileged build user and hand the staged tree to
+    /// it (rootless builds)
+    PreparingBuildUser,
     /// debian/rules build
     Building,
     /// fakeroot debian/rules binary
@@ -63,6 +69,8 @@ impl Phase {
             Phase::ApplyingPatches => "Applying patches",
             Phase::InjectingPackages => "Injecting packages",
             Phase::InstallingBuildDeps => "Installing build dependencies",
+            Phase::ClearingResumeCaches => "Clearing resumed build caches",
+            Phase::PreparingBuildUser => "Preparing the build user",
             Phase::Building => "Building package",
             Phase::ProducingBinaries => "Producing binary packages",
             Phase::RetrievingArtifacts => "Retrieving artifacts",
@@ -82,6 +90,8 @@ impl Phase {
             Phase::ApplyingPatches => "applying_patches",
             Phase::InjectingPackages => "injecting_packages",
             Phase::InstallingBuildDeps => "installing_build_deps",
+            Phase::ClearingResumeCaches => "clearing_resume_caches",
+            Phase::PreparingBuildUser => "preparing_build_user",
             Phase::Building => "building",
             Phase::ProducingBinaries => "producing_binaries",
             Phase::RetrievingArtifacts => "retrieving_artifacts",
@@ -101,6 +111,8 @@ impl Phase {
             "applying_patches" => Phase::ApplyingPatches,
             "injecting_packages" => Phase::InjectingPackages,
             "installing_build_deps" => Phase::InstallingBuildDeps,
+            "clearing_resume_caches" => Phase::ClearingResumeCaches,
+            "preparing_build_user" => Phase::PreparingBuildUser,
             "building" => Phase::Building,
             "producing_binaries" => Phase::ProducingBinaries,
             "retrieving_artifacts" => Phase::RetrievingArtifacts,
@@ -122,6 +134,9 @@ fn default_classifier(phase: Phase) -> Box<dyn Classifier> {
         Phase::InstallingBuildDeps => {
             Box::new(AptInstallClassifier::new("Installing build dependencies"))
         }
+        Phase::ClearingResumeCaches | Phase::PreparingBuildUser => {
+            Box::new(GenericClassifier::new())
+        }
         Phase::Building | Phase::ProducingBinaries => Box::new(MakeClassifier::new()),
         Phase::RetrievingArtifacts => Box::new(GenericClassifier::new()),
     }
@@ -1147,6 +1162,8 @@ mod tests {
             Phase::ApplyingPatches,
             Phase::InjectingPackages,
             Phase::InstallingBuildDeps,
+            Phase::ClearingResumeCaches,
+            Phase::PreparingBuildUser,
             Phase::Building,
             Phase::ProducingBinaries,
             Phase::RetrievingArtifacts,