[NaCl SDK] Fix SDK to have pnacl as default toolchain.

native_client_sdk/src/build_tools/build_sdk.py

Index: native_client_sdk/src/build_tools/build_sdk.py
diff --git a/native_client_sdk/src/build_tools/build_sdk.py b/native_client_sdk/src/build_tools/build_sdk.py
index 1dda093c26cdf8161cbf75f72857cfbe11e498fb..224ecdb0872aed7badce48d0ca90afa344fdeed6 100755
--- a/native_client_sdk/src/build_tools/build_sdk.py
+++ b/native_client_sdk/src/build_tools/build_sdk.py
@@ -949,7 +949,9 @@ def main(args):
     options.build_app_engine = False
     options.tar = True
 
-  toolchains = ['newlib', 'glibc', 'arm', 'pnacl', 'host']
+  # NOTE: order matters here. This will be the order that is specified in the
+  # Makefiles; the first toolchain will be the default.
+  toolchains = ['pnacl', 'newlib', 'glibc', 'arm', 'host']
 
   # Changes for experimental bionic builder
   if options.bionic: