Reduce the size of a release test_shell from 18mb to 13mb.

Reduce the size of a release test_shell from 18mb to 12mb.

- Strip all symbols.  We previously had many exported symbols.

- GC sections.  -fdata/function-sections make sure each piece of code/data has it's own section, since GC works on an entire section.  I will follow up on the V8 build with the same.

- Remove the ident pragmas.  For example, we previously had a string like:
  GCC: (GNU) 4.2.4 (Ubuntu 4.2.4-1ubuntu1)
  Repeated in the .comment section (one for each object?).  This data is just metadata.

[Dean McNamee, 2009-01-26 12:06:41]

This is some simple low hanging stuff.  The ident was only 80k, but it's still
pretty pointless.  The unneeded symbols were the majority ~5mb.

I will follow up someday and try to make real dents into our code / data
sections.

[Dean McNamee, 2009-01-26 17:25:43]

Now 12mb.  Adding Mark.

[sgk, 2009-01-26 17:38:50]

lgtm

[Mark Mentovai, 2009-01-26 17:48:31]

lgtm, good work

[Evan Martin, 2009-01-26 18:12:11]

For random people running random self-compiled binaries, they will no longer be
able to get backtraces from crashes, right?

[Lei Zhang, 2009-01-26 22:21:23]

http://codereview.chromium.org/18586/diff/202/203
File build/SConscript.main (right):

http://codereview.chromium.org/18586/diff/202/203#newcode531
Line 531: linux_env.Append(LINKFLAGS_OPTIMIZED=['-Wl,--gc-sections', '-s'])
FYI, gold does not support --gc-sections.