CMake: Replace generator conditional expressions

OPENGL_LIBRARIES may contain multiple paths, separated by semicolons.
In CMake 3.22.1 this results in an improper list of libraries. The workaround
is to instead clear library paths that are not supposed to be linked.

source/Irrlicht/CMakeLists.txt

@@ -314,24 +314,38 @@ set(link_includes
 	"$<$<BOOL:${USE_X11}>:${X11_INCLUDE_DIR}>"
 )
 
+macro(MAKE_EMPTY_IF_FALSE condition variable)
+	if(NOT DEFINED ${condition} OR NOT ${${condition}})
+		set(${variable} "")
+	endif()
+endmacro()
+
+MAKE_EMPTY_IF_FALSE(USE_SDL2               SDL2_LIBRARIES)
+MAKE_EMPTY_IF_FALSE(OPENGL_DIRECT_LINK     OPENGL_LIBRARIES)
+MAKE_EMPTY_IF_FALSE(OPENGLES_DIRECT_LINK   OPENGLES_LIBRARY)
+MAKE_EMPTY_IF_FALSE(OPENGLES2_DIRECT_LINK  OPENGLES2_LIBRARIES)
+MAKE_EMPTY_IF_FALSE(USE_X11                X11_X11_LIB)
+MAKE_EMPTY_IF_FALSE(USE_X11                X11_Xi_LIB)
+
 set(link_libs
 	"${ZLIB_LIBRARY}"
 	"${JPEG_LIBRARY}"
 	"${PNG_LIBRARY}"
-	"$<$<BOOL:${USE_SDL2}>:${SDL2_LIBRARIES}>"
+	${EGL_LIBRARY}
+	${SDL2_LIBRARIES}
 
-	"$<$<BOOL:${OPENGL_DIRECT_LINK}>:${OPENGL_LIBRARIES}>"
-	"$<$<BOOL:${OPENGLES_DIRECT_LINK}>:${OPENGLES_LIBRARY}>"
-	"$<$<BOOL:${OPENGLES2_DIRECT_LINK}>:${OPENGLES2_LIBRARIES}>"
+	${OPENGL_LIBRARIES}
+	${OPENGLES_LIBRARY}
+	${OPENGLES2_LIBRARIES}
 	${EGL_LIBRARY}
 
 	"$<$<PLATFORM_ID:Android>:-landroid -llog>"
 	${COCOA_LIB}
 	${IOKIT_LIB}
 	"$<$<PLATFORM_ID:Windows>:gdi32>"
 	"$<$<PLATFORM_ID:Windows>:winmm>"
-	"$<$<BOOL:${USE_X11}>:${X11_X11_LIB}>"
-	"$<$<BOOL:${USE_X11}>:${X11_Xi_LIB}>"
+	${X11_X11_LIB}
+	${X11_Xi_LIB}
 )
 
 # Source files