Targetting clang for 32 bit on aarch64

When I try to compile simple compiler test: `int main(void) { return 0; }` clang with -m32 argument it gives such error:
```
clang -m32 test.c
error: unable to create target: 'No available
      targets are compatible with this triple.'
1 error generated.
$ clang -m32 -dumpmachine
arm--linux-android
```

I think it should be possible to target on 32 bit ARM on AArch64 systems. 