使用clang到ARM：错误的链接器

我正在尝试为ARM交叉编译hello world，而我却坚持使用链接。该命令clang-3.8 -target thumbv7em-none--eabi main.c似乎选择了我的系统gcc工具链...而且我认为这不是我真正想要的

➜  /tmp clang-3.8 -target thumbv7em-none--eabi main.c -v
clang version 3.8.0-2ubuntu3 (tags/RELEASE_380/final)
Target: thumbv7em-none--eabi
Thread model: posix
InstalledDir: /usr/bin
 "/usr/lib/llvm-3.8/bin/clang" -cc1 -triple thumbv7em-none--eabi -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name main.c -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -target-cpu cortex-m4 -target-feature +soft-float -target-feature +soft-float-abi -target-feature -neon -target-feature -crypto -target-feature +strict-align -target-abi aapcs -msoft-float -mfloat-abi soft -v -dwarf-column-info -debugger-tuning=gdb -resource-dir /usr/lib/llvm-3.8/bin/../lib/clang/3.8.0 -fdebug-compilation-dir /tmp -ferror-limit 19 -fmessage-length 190 -fallow-half-arguments-and-returns -fno-signed-char -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/main-755f88.o -x c main.c
clang -cc1 version 3.8.0 based upon LLVM 3.8.0 default target x86_64-pc-linux-gnu
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/llvm-3.8/bin/../lib/clang/3.8.0/include
 /usr/include
End of search list.
 "/usr/bin/gcc" -v -o a.out /tmp/main-755f88.o
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 5.3.1-14ubuntu2.1' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 5.3.1 20160413 (Ubuntu 5.3.1-14ubuntu2.1) 
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/5/:/usr/lib/gcc/x86_64-linux-gnu/5/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/5/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/5/:/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/5/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/5/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-o' 'a.out' '-mtune=generic' '-march=x86-64'
 /usr/lib/gcc/x86_64-linux-gnu/5/collect2 -plugin /usr/lib/gcc/x86_64-linux-gnu/5/liblto_plugin.so -plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/5/lto-wrapper -plugin-opt=-fresolution=/tmp/cckaORlW.res -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lc -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s --sysroot=/ --build-id --eh-frame-hdr -m elf_x86_64 --hash-style=gnu --as-needed -dynamic-linker /lib64/ld-linux-x86-64.so.2 -z relro -o a.out /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-gnu/5/crtbegin.o -L/usr/lib/gcc/x86_64-linux-gnu/5 -L/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/5/../../../../lib -L/lib/x86_64-linux-gnu -L/lib/../lib -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/5/../../.. /tmp/main-755f88.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/5/crtend.o /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crtn.o
/usr/bin/ld: /tmp/main-755f88.o: Relocations in generic ELF (EM: 40)
/tmp/main-755f88.o: error adding symbols: File in wrong format
collect2: error: ld returned 1 exit status

```

手动在Internet呼叫链接器中添加一些小伙子，但是最好避免这种情况。

其他推荐--gcc-toolchain=path选项。我尝试了几种路径（/usr/bin/arm-none-eabi-gcc，/usr/lib/gcc/arm-none-eabi/4.9.），但此选项不会影响所有操作。

我还读到clang使用llvm编译期间指定的工具链。但这在我们进行交叉编译时没有意义，不是吗？

有什么想法如何使用clang选项指定交叉链接器吗？