Bug#941817: llvm-toolchain-8: FTBFS on x32

[Thorsten Glaser]

> I’m attaching the patch and am currently building it locally to
> see whether this was all or whether more is needed.

It failed very early with…

[…]
-- Builtin supported architectures:
-- Linker detection: GNU ld
-- Linker detection: GNU ld
-- Builtin supported architectures:
-- check-shadowcallstack does nothing.
-- Sphinx enabled.
-- Found Sphinx: /usr/bin/sphinx-build
-- ISL version: isl-0.20-65-gb822a210
-- Performing Test HAS_ATTRIBUTE_WARN_UNUSED_RESULT
-- Performing Test HAS_ATTRIBUTE_WARN_UNUSED_RESULT - Failed
-- Performing Test HAVE___ATTRIBUTE__
-- Performing Test HAVE___ATTRIBUTE__ - Failed
-- Performing Test HAVE_DECL_FFS
-- Performing Test HAVE_DECL_FFS - Failed
-- Performing Test HAVE_DECL___BUILTIN_FFS
-- Performing Test HAVE_DECL___BUILTIN_FFS - Failed
-- Performing Test HAVE_DECL__BITSCANFORWARD
-- Performing Test HAVE_DECL__BITSCANFORWARD - Failed
CMake Error at tools/polly/lib/External/CMakeLists.txt:91 (message):
  No ffs implementation found

… which is caused by:

cc1: error: unrecognized argument to '-flto=' option: 'thin'

Somehow, the build system applies -flto=thin to the host compiler,
and GCC doesn’t support this flag.

bye,
//mirabilos
-- 
tarent solutions GmbH
Rochusstraße 2-4, D-53123 Bonn • http://www.tarent.de/
Tel: +49 228 54881-393 • Fax: +49 228 54881-235
HRB 5168 (AG Bonn) • USt-ID (VAT): DE122264941
Geschäftsführer: Dr. Stefan Barth, Kai Ebenrett, Boris Esser, Alexander Steeg