Clang toolchain on Linux: compress with XZ, include LLVM Gold plugin.

Clang toolchain on Linux: compress with XZ, include LLVM Gold plugin.

This CL decreases the size of the archive from 28 MB down to 21 MB, by using XZ instead of GZIP. It also includes LLVM Gold plugin for CFI consumption. This is only for Linux.

BUG=chromium:536159, chromium:464797

[krasin, 2015-10-05 19:05:25]

krasin@google.com changed reviewers:
+ hans@chromium.org

[krasin, 2015-10-05 19:07:12]

My latest measurements (using this particular CL) show the size of the archive
to be lower than earlier numbers:

-rw-r----- 1 krasin eng 20550560 Oct  5 11:37 clang-247874-1.tar.xz

I have verified that it already include LLVM Gold plugin. Not sure why did I get
larger numbers previously.

[hans, 2015-10-05 20:53:56]

hans@chromium.org changed reviewers:
+ thakis@chromium.org

[hans, 2015-10-05 20:53:57]

As mentioned before, I'm not signing off on bundling the plugin until I've heard
what Nico says, as he's spoken out against it before. I also want to hear his
thoughts on switching the archive format.

If you need to move faster, https://codereview.chromium.org/1373043003/ is the
way. But this is all old news.


Switching to xz and bundling the plugin should be done in two different patches.

The bundling patch should delete download_gold_plugin.py.

Switching to xz will also require updating the goma push scripts (look for
upload_clang.sh in internal code search).

One potential problem with switching to xz is that it's not supported by the
tarfile module in Chromium's Python version (2.7). That makes it hard to use xz
on Mac and Windows. Using the same format everywhere would be nice. We're moving
towards replacing update.sh with update.py, and having to shell out to xz there
is a little annoying. The savings might be worth it, though.

https://codereview.chromium.org/1375213007/diff/20001/tools/clang/scripts/pac...
File tools/clang/scripts/package.py (right):

https://codereview.chromium.org/1375213007/diff/20001/tools/clang/scripts/pac...
tools/clang/scripts/package.py:239: # Zip up gold plugin on Linux.
Bundling the plugin makes this code unnecessary.

https://codereview.chromium.org/1375213007/diff/20001/tools/clang/scripts/upd...
File tools/clang/scripts/update.sh (right):

https://codereview.chromium.org/1375213007/diff/20001/tools/clang/scripts/upd...
tools/clang/scripts/update.sh:271: unxz < "${CDS_OUTPUT}" | tar -x -C
"${LLVM_BUILD_DIR}"
Maybe just use tar's -J option?

[krasin, 2015-10-05 21:07:02]

krasin@google.com changed reviewers:
- hans@chromium.org

[krasin, 2015-10-05 21:07:21]

Ok, let's wait for Nico.