LLVM/clang ias build fails with unsupported arguments '-mpower4' and '-many' to option 'Wa,'

[Paul Menzel]

Dear Linux folks,

Building Linux with LLVM’s integrated assembler fails with the error 
below [1].

```
$ ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- make LLVM=1 
LLVM_IAS=1 -j72 pseries_defconfig arch/powerpc/kernel/vdso32/gettimeofday.o
...
arch/powerpc/kernel/vdso32/gettimeofday.S:72:8: error: unsupported 
directive '.stabs'
.stabs "_restgpr_31_x:F-1",36,0,0,_restgpr_31_x; .globl _restgpr_31_x; 
_restgpr_31_x:
       ^
arch/powerpc/kernel/vdso32/gettimeofday.S:73:8: error: unsupported 
directive '.stabs'
.stabs "_rest32gpr_31_x:F-1",36,0,0,_rest32gpr_31_x; .globl 
_rest32gpr_31_x; _rest32gpr_31_x:
       ^
```

The LLVM developers are not planning on implementing this, as Stab has 
been succeeded by DWARF [2].


Kind regards,

Paul


[1]: https://github.com/ClangBuiltLinux/linux/issues/1418
[2]: https://bugs.llvm.org/show_bug.cgi?id=31134