add missing headers

Co-authored-by: Rodrigo Faselli <162915171+RF47@users.noreply.github.com>

src/libslic3r/GCode/OrderingStrategies.cpp

@@ -6,6 +6,7 @@
 #include "../ShortestPath.hpp"
 #include "libslic3r/Point.hpp"
 #include "libslic3r/PrintConfig.hpp"
+#include "libslic3r/libslic3r.h"
 
 #include <algorithm>
 #include <cmath>

tests/libslic3r/test_clipper_utils.cpp

@@ -11,8 +11,10 @@
 #include <boost/filesystem.hpp>
 #include <utility>
 #include <vector>
+#include <cstdlib>
 
 #include <catch2/catch_test_macros.hpp>
+#include <catch2/generators/catch_generators.hpp>
 #include <catch2/catch_approx.hpp>
 #include "libslic3r/ClipperUtils.hpp"
 #include "libslic3r/ExPolygon.hpp"

tests/libslic3r/test_kdtree.cpp

@@ -3,6 +3,11 @@
 #include <numeric>
 #include <random>
 #include <vector>
+#include <algorithm>
+#include <cstddef>
+
+#include <catch2/catch_test_macros.hpp>
+#include <catch2/generators/catch_generators.hpp>
 
 #include "libslic3r/KDTreeIndirect.hpp"
 #include "libslic3r/Point.hpp"