NaCl: Copy only the needed IRT architectures into the build directory

NaCl: Copy only the needed IRT architectures into the build directory

This fixes various Linux packages/zip files of Chrome/Chromium so that
they only include the IRT for the target architecture.

Originally I thought it would be fine to copy both the x86-32 and
x86-64 versions of the IRT library into the build directory, on the
grounds that the Mac/Linux packaging steps would only copy the
versions they needed from there.  (On Windows we need both so it
doesn't matter.)  And indeed, this is fine on Mac where the app dir is
created by logic in chrome/chrome_dll.gypi and everyone uses that.

For Linux, however, there are various packaging steps that take files
directly from out/Release or out/Debug.  This includes:

 * The Buildbot config, which creates zip file snapshots which are
   uploaded here:
   http://build.chromium.org/f/chromium/snapshots/Linux_x64/
   The script responsible for doing this is in the Buildbot config:
   http://src.chromium.org/viewvc/chrome/trunk/tools/build/scripts/slave/chromium/archive_build.py?revision=84592&view=markup
   and this uses the file list in chrome/tools/build/linux/FILES.

 * The .deb and .rpm creators that are invoked from
   chrome/chrome_installer.gypi via linux_packages_all.  This Gyp file
   invokes scripts that live in the private repo:
     installer/linux/internal/debian/build.sh
     installer/linux/internal/rpm/build.sh
   Yesterday I had to change
     installer/linux/internal/common/installer.include
   so that nacl_irt_{32,64}.nexe would get copied by these scripts,
   but it ended up copying both versions.  The conditionals I added in
   chrome/chrome_installer.gypi on 9th May for
   packaging_files_binaries are seemingly not used.

The easiest way to fix these is to be more selective about what we put
into out/{Release,Build} to start with.

BUG=84143
TEST=trybots (I inspected the "compile" steps to ensure that the right
  IRT binaries get copied in them)

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=86967

[bradn, 2011-05-27 01:27:26]

LGTM

[bradn, 2011-05-27 01:27:27]

LGTM