Bug#979656: Patch for llvm-toolchain-7

[Santiago Vila]

Additional note: I actually tested the patches on two different
machines to be sure (with and without the patch) and built the package
in interactive mode (i.e. dpkg-buildpackage, not sbuild).

In the machine where I didn't apply the patch, this is what was shown
on screen at the moment of hangup:


[100%] Running lld test suite
cd
/home/sanvila/llvm-toolchain-7-7.0.1/build-llvm/tools/clang/stage2-bins/tools/lld/test
&& /usr/bin/python2.7
/home/sanvila/llvm-toolchain-7-7.0.1/build-llvm/tools/clang/stage2-bins/./bin/llvm-lit
-sv --param
lld_site_config=/home/sanvila/llvm-toolchain-7-7.0.1/build-llvm/tools/clang/stage2-bins/tools/lld/test/lit.site.cfg
--param
lld_unit_site_config=/home/sanvila/llvm-toolchain-7-7.0.1/build-llvm/tools/clang/stage2-bins/tools/lld/test/Unit/lit.site.cfg
/home/sanvila/llvm-toolchain-7-7.0.1/build-llvm/tools/clang/stage2-bins/tools/lld/test
                                -- Testing: 1808 tests, 1 threads --
				 92%
[========================================================================------]
ETA: 00:00:10
lld :: mach-o/write-final-sections.yaml


I agree that this is for historical interest only, as I guess that
nobody here wants to investigate the failure, and everybody here
probably agrees that disabling the tests is a much better course of
action.

Thanks.