Core: Move PyCXX library to src/3rdParty.

src/Mod/TechDraw/App/CMakeLists.txt

@@ -9,6 +9,7 @@ include_directories(
     ${OCC_INCLUDE_DIR}
     ${ZIPIOS_INCLUDES}
     ${ZLIB_INCLUDE_DIR}
+    ${PYCXX_INCLUDE_DIR}
     ${Python3_INCLUDE_DIRS}
     ${XercesC_INCLUDE_DIRS}
 )

src/Mod/TechDraw/Gui/CMakeLists.txt

@@ -18,6 +18,7 @@ include_directories(
     ${CMAKE_CURRENT_SOURCE_DIR}
     ${Boost_INCLUDE_DIRS}
     ${COIN3D_INCLUDE_DIRS}
+    ${PYCXX_INCLUDE_DIR}
     ${Python3_INCLUDE_DIRS}
     ${OCC_INCLUDE_DIR}
     ${ZIPIOS_INCLUDES}