Move runPostBuildHook out of DerivationBuilder

It is suppposed to be "post build" not "during the build" after all. Its
location now matches that for the hook case (see elsewhere in
`DerivationdBuildingGoal`).

It was in a try-catch before, and now it isn't, but I believe that it is
impossible for it to throw `BuildError`, which is sufficient for this
code motion to be correct.

src/libstore/build/derivation-building-goal.cc

@@ -148,6 +148,9 @@ std::string showKnownOutputs(const StoreDirConfig & store, const Derivation & dr
     return msg;
 }
 
+static void runPostBuildHook(
+    const StoreDirConfig & store, Logger & logger, const StorePath & drvPath, const StorePathSet & outputPaths);
+
 /* At least one of the output paths could not be
    produced using a substitute.  So we have to build instead. */
 Goal::Co DerivationBuildingGoal::gaveUpOnSubstitution()
@@ -810,6 +813,11 @@ Goal::Co DerivationBuildingGoal::tryToBuild()
         outputLocks.unlock();
         co_return done(std::move(ste->first), {}, std::move(ste->second));
     } else if (auto * builtOutputs = std::get_if<1>(&res)) {
+        StorePathSet outputPaths;
+        for (auto & [_, output] : *builtOutputs)
+            outputPaths.insert(output.outPath);
+        runPostBuildHook(worker.store, *logger, drvPath, outputPaths);
+
         /* It is now safe to delete the lock files, since all future
            lockers will see that the output paths are valid; they will
            not create new lock files with the same names as the old
@@ -823,7 +831,7 @@ Goal::Co DerivationBuildingGoal::tryToBuild()
 #endif
 }
 
-void runPostBuildHook(
+static void runPostBuildHook(
     const StoreDirConfig & store, Logger & logger, const StorePath & drvPath, const StorePathSet & outputPaths)
 {
     auto hook = settings.postBuildHook;

src/libstore/include/nix/store/build/derivation-building-misc.hh

@@ -49,9 +49,6 @@ struct InitialOutput
     std::optional<InitialOutputStatus> known;
 };
 
-void runPostBuildHook(
-    const StoreDirConfig & store, Logger & logger, const StorePath & drvPath, const StorePathSet & outputPaths);
-
 /**
  * Format the known outputs of a derivation for use in error messages.
  */

src/libstore/include/nix/store/build/derivation-goal.hh

@@ -14,9 +14,6 @@ namespace nix {
 
 using std::map;
 
-/** Used internally */
-void runPostBuildHook(Store & store, Logger & logger, const StorePath & drvPath, const StorePathSet & outputPaths);
-
 /**
  * A goal for realising a single output of a derivation. Various sorts of
  * fetching (which will be done by other goal types) is tried, and if none of

src/libstore/unix/build/derivation-builder.cc

@@ -506,11 +506,6 @@ std::variant<std::pair<BuildResult::Status, Error>, SingleDrvOutputs> Derivation
            being valid. */
         auto builtOutputs = registerOutputs();
 
-        StorePathSet outputPaths;
-        for (auto & [_, output] : builtOutputs)
-            outputPaths.insert(output.outPath);
-        runPostBuildHook(store, *logger, drvPath, outputPaths);
-
         /* Delete unused redirected outputs (when doing hash rewriting). */
         for (auto & i : redirectedOutputs)
             deletePath(store.Store::toRealPath(i.second));