This is in an effort to fix the following build failure shown by
chromium:
clang++: error: no such file or directory: '/nix/store/fhd89wrmkx6nflzjk0d6waz70bk3zc4i-clang-wrapper-12.0.0/resource-root/share/cfi_blacklist.txt'
As it turns out a change introduced via the gnu-install-dirs.patch
caused `add_compiler_rt_resource_file` to install resource files to
$dev/include (FULL_INCLUDEDIR) instead of $out/share (FULL_DATADIR)
which in turn meant that the clang wrappers we had didn't link those
files to its resource root at all.
Alternative fix to this would have been to link
compiler-rt.dev/include/*.txt to the wrappers resource-root/share as
well, but since this was handled inconsistently across the patch anyways
(the dfsan list is installed correctly), opt to handle this
consistently within the patch.
llvmPackages_{5,6} install the resource files to a completely different
location and need separate investigation.