clang/mac: Bundle libc++.dylib with clang.

clang/mac: Bundle libc++.dylib with clang.

clang now uses c++11, which on OS X means it depends on libc++.
OS X 10.6 doesn't have libc++ yet, but some bots still are on 10.6 and
upgrading them will take a bit longer. Bundle libc++ with the clang package,
and set rpaths so that both clang and plugins refer to the bundled libc++
instead of /usr/lib/libc++.1.dylib.

(System libraries will still cause libstdc++ to be loaded as well. Since libc++
keeps its symbols in std::__1:: and aliases everything to that, loading libc++
and libstdc++ in the same process is safe.)

Also don't set MACOSX_DEPLOYMENT_TARGET while building the bootstrap
compiler (Xcode's clang complains when using -stdlib=libc++ when targeting
10.6 or older; open-source luckily doesn't for some reason).

Also pass -isysroot; when building on OS X 10.9, /usr/include doesn't exist
unless the command line tools are installed.

BUG=358500
TEST=Run package.sh (with a tweaked clang revision, to not clobber an
existing package). Upload produced tgz file somewhere, download it on
a 10.6 box. Clang should run.

R=hans@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=260908

[Nico, 2014-04-01 03:42:45]

This seems to do the trick (only did very light testing. This can build a "hello
world" on a 10.6 box, and it can load the two plugin dylibs on a 10.6 box.)

[hans, 2014-04-01 15:59:18]

lgtm

https://codereview.chromium.org/218613009/diff/210001/tools/clang/scripts/upd...
File tools/clang/scripts/update.sh (right):

https://codereview.chromium.org/218613009/diff/210001/tools/clang/scripts/upd...
tools/clang/scripts/update.sh:1039: # Build libc++.dylib while some bots are
still on OS X 10.6.
i never built libc++, but i assume its build system doesn't work for us since it
looks like you're hand rolling the compilation below?

[Nico, 2014-04-01 18:26:18]

Thanks!

https://codereview.chromium.org/218613009/diff/210001/tools/clang/scripts/upd...
File tools/clang/scripts/update.sh (right):

https://codereview.chromium.org/218613009/diff/210001/tools/clang/scripts/upd...
tools/clang/scripts/update.sh:1039: # Build libc++.dylib while some bots are
still on OS X 10.6.
On 2014/04/01 15:59:19, hans wrote:
> i never built libc++, but i assume its build system doesn't work for us since
it
> looks like you're hand rolling the compilation below?

libc++'s build system is a shell script called "buildit" that roughly does "cc
-c src/*.cpp" with the flags I'm using here. (There's now a cmake build of it,
but not of libc++abi as far as I know, and I need to link both libc++ and
libc++abi into the same dylib. libc++'s buildit uses a "reexport symbols" trick
for this, but that trick doesn't work when targeting older os x versions.)

[Nico, 2014-04-01 18:31:50]

Committed patchset #12 manually as r260908 (tree was closed).