Fix Clang warning in ImGui

Author: ChrisThrasher

CMakeLists.txt

@@ -66,10 +66,12 @@ include(GNUInstallDirs)
 add_library(ImGui-SFML imgui-SFML.cpp ${IMGUI_SOURCES})
 add_library(ImGui-SFML::ImGui-SFML ALIAS ImGui-SFML)
 target_include_directories(ImGui-SFML PUBLIC
-  $<BUILD_INTERFACE:${IMGUI_INCLUDE_DIR}>
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>
   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
 )
+target_include_directories(ImGui-SFML SYSTEM PUBLIC
+  $<BUILD_INTERFACE:${IMGUI_INCLUDE_DIR}>
+)
 target_link_libraries(ImGui-SFML PUBLIC SFML::Graphics OpenGL::GL)
 if(WIN32 AND MINGW)
   target_link_libraries(ImGui-SFML PUBLIC imm32)