Pin Clang revision to r170392 for ASan Mac builders.

Pin Clang revision to r170392 for ASan Mac builders.
This temporary change introduces the --is-asan-mac-builder flag and a blacklist of OSX hosts building ASan
on the Chromium waterfall. If either the flag is set or `uname -n` is in the list, older Clang is used.

BUG=170629, 174873
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=181918

[hans, 2013-02-12 11:46:09]

Do we know that these vm's are used exclusively for asan builders?

Or could it happen that vm${num}-m4.golo is also used for a non-asan buildbot?

[Alexander Potapenko, 2013-02-12 11:48:54]

On 2013/02/12 11:46:09, hans wrote:
> Do we know that these vm's are used exclusively for asan builders?
> 
> Or could it happen that vm${num}-m4.golo is also used for a non-asan buildbot?
vm633-m1 is an exclusive ASan Mac Builder
vm{600-655}-m4 are machines from the trybot pool. According to
http://src.chromium.org/viewvc/chrome?view=rev&revision=168096, they're used
exclusively for ASan now.

[Alexander Potapenko, 2013-02-12 11:49:12]

+Nico

[hans, 2013-02-12 11:53:47]

This feels horribly fragile, so I hope we can get rid off it very soon.

lgtm

[Nico, 2013-02-12 16:51:24]

:-/

When we did something like this for Android during android/clang bring-up, we
looked at the path instead of the hostname. But that's horrible too, so I guess
this is fine. Hopefully it goes away very soon.

https://codereview.chromium.org/12210139/diff/6001/tools/clang/scripts/update.sh
File tools/clang/scripts/update.sh (right):

https://codereview.chromium.org/12210139/diff/6001/tools/clang/scripts/update...
tools/clang/scripts/update.sh:61: is_asan_mac_builder=yes
This is in already, but in the future when doing something like this please

a) Add a comment that calls this out as a temporary workaround. There's a
comment with a link to a bug below, but it's hidden and it's not obvious from
the code that this is temporary.

b) Make the UI so that it's obvious that is temporary. In this case, you could
call the flag "--asan-mac-builder-hackfix" or similar.

[Nico, 2013-02-12 22:59:30]

https://codereview.chromium.org/12210139/diff/8002/tools/clang/scripts/update.sh
File tools/clang/scripts/update.sh (right):

https://codereview.chromium.org/12210139/diff/8002/tools/clang/scripts/update...
tools/clang/scripts/update.sh:93: if [[ -n is_asan_mac_builder ]] ||
on_asan_mac_host; then
This must say ${is_asan_mac_builder}. As is, this _always_ uses the old clang,
which means the current roll landed without any testing by the bots. (On the
plus side, it's not live yet.)

I'll leave it to you and Hans to sort this out (I recommend reverting the clang
roll, then fixing this script, then hitting cq+ on the clang roll again.)

I'm sorry for missing this, but please do test patches locally before sending
them out and relying on reviewers to catch mistakes.