[PATCH v2] configure: Avoid clobbering x18 on arm64 when building with clang

[André Hentschel]

Am 23.06.2017 um 20:22 schrieb Martin Storsjö:
> On Fri, 23 Jun 2017, André Hentschel wrote:
> 
>> Am 23.06.2017 um 11:38 schrieb Martin Storsjö:
>>> On Fri, 23 Jun 2017, Alexandre Julliard wrote:
>>>
>>>> Martin Storsjö <martin at martin.st> writes:
>>>>
>>> I'm not sure if that discussion resulted in something else somewhere - if I'm just lucky that it has happened to work for me so far (but could break randomly if gcc would happen to use x18 anywhere in the called system libraries, and just clang seems to be using it more often so I only ran into it with clang?), or if something really was changed elsewhere with respect to this. André, can you fill us in on this matter?
>>
>> So your Wine build crashes even when running Wines cmd/winecfg/...? Is that fixed by removing the assembler line in dlls/ntdll/signal_arm64.c:signal_init_thread ?

While I signed off your patch, could you please try what happens without reserve-x18 and without the assemblerline i referenced?