Build: suppress warnings from 3rd party libraries

Warnings from 3rd parties are not relevant and are only polluting the warning output. Marking these libraries as SYSTEM suppresses warning.

https://gcc.gnu.org/onlinedocs/cpp/Invocation.html#index-I
https://gcc.gnu.org/onlinedocs/cpp/System-Headers.html

src/Mod/JtReader/App/CMakeLists.txt

@@ -4,6 +4,10 @@ set(JTREADER_TKJT_LIBRARIES CACHE FILEPATH  "File path to TKJT library")
 include_directories(
     ${CMAKE_BINARY_DIR}
     ${CMAKE_CURRENT_BINARY_DIR}
+)
+
+include_directories(
+    SYSTEM
     ${Boost_INCLUDE_DIRS}
     ${OCC_INCLUDE_DIR}
     ${ZLIB_INCLUDE_DIR}
@@ -33,7 +37,7 @@ SET(JtReader_SRCS
 
 if (EXISTS "${JTREADER_TKJT_INCLUDE_DIRS}/JtData_Object.hxx")
     add_definitions(-DJTREADER_HAVE_TKJT)
-    include_directories(${JTREADER_TKJT_INCLUDE_DIRS})
+    include_directories(SYSTEM ${JTREADER_TKJT_INCLUDE_DIRS})
     list (APPEND JtReader_LIBS
         ${JTREADER_TKJT_LIBRARIES}
     )