Reduce lengthy compile commands by removing dup include-paths

src/dds/build/plan/compile_file.cpp

 #include <dds/util/signal.hpp>
 #include <dds/util/time.hpp>
 
+#include <range/v3/algorithm/sort.hpp>
+#include <range/v3/algorithm/unique.hpp>
+
 #include <string>
 #include <vector>
 
         extend(spec.external_include_dirs, env.ureqs.include_paths(use));
     }
     extend(spec.definitions, _rules.defs());
+    // Avoid huge command lines by shrinking down the list of #include dirs
+    sort_unique_erase(spec.external_include_dirs);
+    sort_unique_erase(spec.include_dirs);
     return env.toolchain.create_compile_command(spec, dds::fs::current_path(), env.knobs);
 }
 

src/dds/util/algo.hpp

     c.insert(c.end(), il.begin(), il.end());
 }
 
+template <typename Container>
+void unique_erase(Container& c) noexcept {
+    c.erase(std::unique(c.begin(), c.end()), c.end());
+}
+
+template <typename Container>
+void sort_unique_erase(Container& c) noexcept {
+    std::sort(c.begin(), c.end());
+    unique_erase(c);
+}
+
 template <typename T>
 using ref_vector = std::vector<std::reference_wrapper<T>>;
 
-}  // namespace dds
+}  // namespace dds