我正在尝试为 iPhone 构建 linphone SDK，并且我已经安装了所有的 perquisites 和依赖项。当我尝试制作 SDK（使用make all命令）时，出现以下错误：
make -f builder-iphone-simulator.mk enable_gpl_third_parties=yes enable_zrtp=no enable_opus=yes enable_debug=no enable_ffmpeg=yes all \
&& make -f builder-iphone-os.mk enable_gpl_third_parties=yes enable_zrtp=no enable_opus=yes enable_debug=no enable_ffmpeg=yes all \
&& make -f builder-iphone-os.mk host=armv7s-apple-darwin enable_gpl_third_parties=yes enable_zrtp=no enable_opus=yes enable_debug=no enable_ffmpeg=yes all \
&& make -f builder-iphone-os.mk delivery-sdk
mkdir -p /Users/Unkn0wn/Developer/GIT/linphone-iphone/submodules/build/..//../liblinphone-sdk/i386-apple-darwin/include
mkdir -p /Users/Unkn0wn/Developer/GIT/linphone-iphone/submodules/build/..//../liblinphone-sdk/i386-apple-darwin/lib/pkgconfig
make[1]: *** No rule to make target `/Users/Unkn0wn/Developer/GIT/linphone-iphone/submodules/build/..//externals/polarssl/Makefile', needed by `update-tree'. Stop.
make: *** [build] Error 2
任何人都知道问题是什么，我该怎么办？