（Ubuntu 16.04.1）
默认情况下，在16.04.1上，clang为5.4选择gcc工具链。不幸的是，我有一个要求 5.0之前的ABI 的库，并且我无权访问源代码，也没有实现者发布新版本。我一直在尝试使用--gcc-toolchain选项，但是无法正常工作。（ctrbegin.o和crtend.o在链接上没有正确的前缀。）
$ clang++-3.8 -v -print-search-dirs
clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/5.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/6.0.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.0.0
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate …