fix(incremental): relink when a C or CUDA object is rebuilt

The C compile loop sets no repack flag, and the "is any object newer than
the archive" sweep only walked interfaces and implementations. So editing
a .c recompiled its object and then linked nothing: the archive and the
executable kept the previous one. Surfaced by the header-change test,
where a rebuilt counter.c produced a binary still printing the old value.

implementations/Crafter.Build-Clang.cpp

@@ -1109,6 +1109,21 @@ BuildResult Crafter::Build(Configuration& config, std::unordered_map<fs::path, s
                         }
                     }
                 }
+                // C and CUDA objects are archive members too, and their compile
+                // loop above is the only thing that knows it rebuilt one — it
+                // sets no repack flag, so without this a .c edit recompiled the
+                // object and then linked nothing.
+                if (!buildResult.repack) {
+                    auto sourceObjNewer = [&](const std::vector<fs::path>& sources) {
+                        for (const fs::path& source : sources) {
+                            if (objNewer(buildDir / std::format("{}_source.o", source.filename().string()))) return true;
+                        }
+                        return false;
+                    };
+                    if (sourceObjNewer(config.cFiles) || sourceObjNewer(config.cuda)) {
+                        buildResult.repack = true;
+                    }
+                }
             }
         }
     }