Revert 169532 - Beginnings of moving more stuff from build_sdk.py to GYP.

Revert 169532 - Beginnings of moving more stuff from build_sdk.py to GYP.

Adds a new target to all.gyp: chromium_builder_nacl_sdk
Adds a native_client_sdk gyp file: it depends on nacl_core_sdk from the
native_client repo, but also builds and copies ppapi libraries to the toolchain
directories.

Retry of https://codereview.chromium.org/11413075/.
This one failed because I didn't check for disable_nacl=1.

Which was a retry of http://codereview.chromium.org/11299081/.
Which was a retry of http://codereview.chromium.org/11363045/.
Failed both of these times because of a separate NaCl build issue that was
resolved by http://crrev.com/168621.

BUG=none
TBR=noelallen@chromium.org
----------------------------------------------
Broke x64 build:
http://build.chromium.org/p/chromium.chrome/builders/Google%20Chrome%20Linux%20x64/builds/35117

Review URL: https://chromiumcodereview.appspot.com/11316139

TBR=binji@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=169537