Scons: Simplify setup of ARM trusted env
Scons: Simplify setup of ARM trusted env

Don't copy settings into the global os.environ unnecessarily.  My aim
here is to remove the global side effects from the arch-specific env
setup code so that I can move it into a function.

Remove obsolete references to tools/llvm/setup_arm_untrusted_toolchain.sh
and the NACL_SDK_CC env var.

BUG=http://code.google.com/p/nativeclient/issues/detail?id=1988
TEST=trybots

Review URL: http://codereview.chromium.org/7390021

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@6101 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client