only add rpath to the executable, if custom library paths are used

openEMS does not need to explicitly link to libCGAL. libCSXCAD does this already.

openEMS.pro

@@ -77,6 +77,8 @@ win32 {
     # CSXCAD
     isEmpty(CSXCAD_ROOT) {
         CSXCAD_ROOT = /usr
+    } else {
+        QMAKE_LFLAGS += \'-Wl,-rpath,$$CSXCAD_ROOT/lib\'
     }
     INCLUDEPATH += $$CSXCAD_ROOT/include/CSXCAD
     LIBS += -L$$CSXCAD_ROOT/lib -lCSXCAD
@@ -86,7 +88,6 @@ win32 {
     LIBS += -ltinyxml
     DEFINES += TIXML_USE_STL
     LIBS += -lboost_thread-mt
-    LIBS += -lCGAL
     # hdf5 (and mpi for parallel hdf5)
     LIBS += -lhdf5_hl -lhdf5
     LIBS += -lmpi -lmpi_cxx
@@ -102,7 +103,6 @@ win32 {
         -lvtkIO \
         -lvtksys \
         -lvtkFiltering
-    QMAKE_LFLAGS += \'-Wl,-rpath,\$$ORIGIN/../CSXCAD\'
 }
 
 # vtk includes deprecated header files; silence the corresponding warning