[LIT] Allow for executeCommand to take the stdin input.
[LIT] Allow for executeCommand to take the stdin input.

Summary: This patch allows executeCommand to pass a string to the processes stdin.

Reviewers: ddunbar, jroelofs

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11332

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@242631 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm