Trusted ARM compiler: Use Ubuntu's package archive
Trusted ARM compiler: Use Ubuntu's package archive

archive.ubuntu.com is a more standard location for Ubuntu packages
than mirror.pnl.gov.

Plus, I was getting "503: Service Unavailable" errors from
mirror.pnl.gov when I tried to install the ARM packages earlier today.

BUG=none
TEST=ran the installer locally

Review URL: https://chromiumcodereview.appspot.com/9706078

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@8039 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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