Disable all warnings when compiling NSS.

Disable all warnings when compiling NSS.

Disabling individual warnings when compiling NSS no longer works, because
some warnings that cannot be disabled individually are now generated.

BUG=dartbug.com/13064
R=sgjesse@google.com

Committed: https://code.google.com/p/dart/source/detail?r=27190

[Bill Hesse, 2013-09-05 09:24:51]

Some NSS compilation warnings cannot be disabled individually, so we must use -w
to make the Dart build warning-free.  Tested with gcc, clang, visual studio,
xcode, ninja.

I also asked upstream about fixing the three lines that can't be suppressed with
individual warning suppressions.

[Søren Gjesse, 2013-09-05 09:32:10]

lgtm

[Bill Hesse, 2013-09-05 10:56:26]

Added a -w flag to the xcode build.

[Søren Gjesse, 2013-09-05 10:57:40]

lgtm

How about Android?

[Bill Hesse, 2013-09-05 11:07:34]

On 2013/09/05 10:57:40, Søren Gjesse wrote:
> lgtm
> 
> How about Android?

We don't build NSS on Android.  I have a CL out to do that, but it is not
committed.  There are warnings in third_party/jscre compilation on Android.

[Bill Hesse, 2013-09-05 11:09:10]

Committed patchset #2 manually as r27190 (presubmit successful).