Re: Problems with arm64 compat vdso

[Nick Desaulniers]

Hi Vincenzo,
We also are having issues building the cross vDSO with Clang:
https://github.com/ClangBuiltLinux/linux/issues/595

It seems that `LINUXINCLUDE` in arch/arm64/kernel/vdso32/Makefile is including
arm64 headers in the arm part of the vdso32 build, which causes Clang to error
on the arm64 inline asm constraints being used in arm64.

I think if the issue Will described is fixed, it will be simpler for us to fix
the rest to get it to build w/ Clang.

https://github.com/ClangBuiltLinux/linux/issues/595#issuecomment-509874891
is the basis of such a patch.

Clang ships with all backends on by default, and uses a `-target <triple>` to
cross compile; so the idea of passing two cross compiler binaries for a compat
vDSO build doesn't really apply to Clang.