Mark Julia headers as SYSTEM to silence warnings from Julia headers (#198)

Author: halleysfifthinc

CMakeLists.txt

@@ -140,6 +140,8 @@ add_library(${JLCXX_TARGET} SHARED ${JLCXX_SOURCES} ${JLCXX_HEADERS})
 target_include_directories(${JLCXX_TARGET} PUBLIC
   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
   $<BUILD_INTERFACE:${JLCXX_INCLUDE_DIR}>
+)
+target_include_directories(${JLCXX_TARGET} SYSTEM PUBLIC
   "$<BUILD_INTERFACE:${Julia_INCLUDE_DIRS}>"
 )
 
@@ -150,6 +152,8 @@ add_library(${JLCXX_STL_TARGET} SHARED ${JLCXX_STL_SOURCES} ${JLCXX_STL_HEADERS}
 target_include_directories(${JLCXX_STL_TARGET} PUBLIC
   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
   $<BUILD_INTERFACE:${JLCXX_INCLUDE_DIR}>
+)
+target_include_directories(${JLCXX_TARGET} SYSTEM PUBLIC
   "$<BUILD_INTERFACE:${Julia_INCLUDE_DIRS}>"
 )
 target_link_libraries(${JLCXX_STL_TARGET} ${JLCXX_TARGET} $<BUILD_INTERFACE:${Julia_LIBRARY}>)