diff -up openscad-openscad-2019.01-RC2/openscad.pro.polyclipping openscad-openscad-2019.01-RC2/openscad.pro
--- openscad-openscad-2019.01-RC2/openscad.pro.polyclipping	2019-02-15 14:14:00.356626672 -0500
+++ openscad-openscad-2019.01-RC2/openscad.pro	2019-02-15 14:14:19.488249681 -0500
@@ -559,8 +559,7 @@ SOURCES += src/ext/lodepng/lodepng.cpp
 HEADERS += src/ext/lodepng/lodepng.h
            
 # ClipperLib
-SOURCES += src/ext/polyclipping/clipper.cpp
-HEADERS += src/ext/polyclipping/clipper.hpp
+LIBS += -lpolyclipping
 
 # libtess2
 INCLUDEPATH += src/ext/libtess2/Include
diff -up openscad-openscad-2019.01-RC2/src/clipper-utils.h.polyclipping openscad-openscad-2019.01-RC2/src/clipper-utils.h
--- openscad-openscad-2019.01-RC2/src/clipper-utils.h.polyclipping	2019-02-15 14:14:31.068021503 -0500
+++ openscad-openscad-2019.01-RC2/src/clipper-utils.h	2019-02-15 14:14:49.640655527 -0500
@@ -1,6 +1,6 @@
 #pragma once
 
-#include "ext/polyclipping/clipper.hpp"
+#include <polyclipping/clipper.hpp>
 #include "Polygon2d.h"
 
 namespace ClipperUtils {
diff -up openscad-openscad-2019.01-RC2/src/libsvg/shape.h.polyclipping openscad-openscad-2019.01-RC2/src/libsvg/shape.h
--- openscad-openscad-2019.01-RC2/src/libsvg/shape.h.polyclipping	2019-02-15 15:03:16.651372730 -0500
+++ openscad-openscad-2019.01-RC2/src/libsvg/shape.h	2019-02-15 15:03:26.240183783 -0500
@@ -34,7 +34,7 @@
 #include <Eigen/Geometry>
 
 #include "util.h"
-#include "ext/polyclipping/clipper.hpp"
+#include <polyclipping/clipper.hpp>
 
 namespace libsvg {