The patch files need to be updated. 
I have an updated copy to use at https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/912448.

This bug has an owner, thus, it's been triaged. Changing status to "assigned".

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/5b1c8bff1b83bfd9b4ca2c878e0c73271c430289

commit 5b1c8bff1b83bfd9b4ca2c878e0c73271c430289
Author: Luis A. Lozano <llozano@google.com>
Date: Thu Aug 09 19:21:51 2018

[llvm]: roll to version r333878

Testing is captured in
https://docs.google.com/spreadsheets/d/1wca9iIEzv59WY87D_ndRpjIPtTw8gCxh7-xb_mrc-PI/edit#gid=0

BUG=chromium:858896, chromium:840971 
TEST=See testing matrix.

Change-Id: Id609cc92d632d3c1fefff70041076796df95c8c6
Reviewed-on: https://chromium-review.googlesource.com/1168987
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Trybot-Ready: Manoj Gupta <manojgupta@chromium.org>
Trybot-Ready: Luis Lozano <llozano@chromium.org>
Commit-Queue: Luis Lozano <llozano@chromium.org>
Tested-by: Luis Lozano <llozano@chromium.org>

[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-devel/llvm/files/cherry/1b2e8fb0ce651da2d47b98c33b29c0f42a080f13.patch
[rename] https://crrev.com/5b1c8bff1b83bfd9b4ca2c878e0c73271c430289/sys-libs/libcxxabi/libcxxabi-7.0.0-r1.ebuild
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-libs/libcxx/files/libcxx-4.0-xlocale.patch
[rename] https://crrev.com/5b1c8bff1b83bfd9b4ca2c878e0c73271c430289/sys-libs/llvm-libunwind/llvm-libunwind-7.0_pre333878-r1.ebuild
[rename] https://crrev.com/5b1c8bff1b83bfd9b4ca2c878e0c73271c430289/sys-libs/compiler-rt/compiler-rt-7.0_pre333878-r1.ebuild
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-devel/llvm/files/cherry/d5ae6a3f71cbd25e2367c56e1d452bcff16c8324.patch
[rename] https://crrev.com/5b1c8bff1b83bfd9b4ca2c878e0c73271c430289/sys-libs/libcxx/libcxx-7.0.0-r1.ebuild
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-libs/libcxxabi/files/libcxxabi-use-libgcc_eh.patch
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-devel/llvm/files/llvm-7.0-dwo-name.patch
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-devel/llvm/files/cherry/b25fd2f921ce952213dcf1ac047150996c1d15c2.patch
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-devel/llvm/files/cherry/ff5baa90d1d3b92c0cffb3a7b1060088d8dcf82b.patch
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-devel/llvm/files/cherry/44b4b3a25821d2024d98417752844a0809ecd204.patch
[rename] https://crrev.com/5b1c8bff1b83bfd9b4ca2c878e0c73271c430289/sys-devel/clang/clang-7.0_pre333878_p20180808-r1.ebuild
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-libs/libcxx/files/libcxx-use-libgcc_eh.patch
[rename] https://crrev.com/5b1c8bff1b83bfd9b4ca2c878e0c73271c430289/sys-devel/lld/lld-7.0_pre333878-r1.ebuild
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-libs/compiler-rt/files/cherry/1b2e8fb0ce651da2d47b98c33b29c0f42a080f13.patch
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-devel/llvm/files/clang-7.0-flto-objcopy.patch
[rename] https://crrev.com/5b1c8bff1b83bfd9b4ca2c878e0c73271c430289/sys-devel/llvm/llvm-7.0_pre333878_p20180808-r1.ebuild
[delete] https://crrev.com/0840f132079900415f1e2e3d8bd3f7f5eea6dd43/sys-devel/llvm/files/cherry/23ea169fe0e4316bf621c6a690900c8a7d9f8707.patch

libc++ was updated in https://chromium-review.googlesource.com/1168987