[lit] Factor out separate methods for parallel and serial execution
[lit] Factor out separate methods for parallel and serial execution

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@375054 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm