Rearrange the build order to better accommodate parallel build by reducing

Rearrange the build order to better accommodate parallel build by reducing
memory pressure. This order spaces out large executables with small ones in
between so that in a -j2 or -j3 build, it only attempts to build only one
large executable at time. If you're doing -j4, you probably have enuogh
memory anyway.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29835 91177308-0d34-0410-b5e6-96231b3b80d8