Building both ia32 and x64 in the sdk build.

We recently changed the chrome build so that nacl binaries of both 32 and 64
bit type are not built unless needed.
The sdk had assumed both arches are built as a side effect.

Building both arches in the sdk.

BUG=None
TEST=local
R=binji@chromium.org

Review URL: https://codereview.chromium.org/590523002

Cr-Commit-Position: refs/heads/master@{#296240}

native_client_sdk/src/build_tools/build_sdk.py

@@ -572,6 +572,7 @@ def BuildStepBuildToolchains(pepperdir, toolchains):
 
   if set(toolchains) & set(['glibc', 'newlib']):
     GypNinjaBuild_PPAPI('ia32', GYPBUILD_DIR)
+    GypNinjaBuild_PPAPI('x64', GYPBUILD_DIR)
 
   if 'arm' in toolchains:
     GypNinjaBuild_PPAPI('arm', GYPBUILD_DIR + '-arm')