[dotest] Disable color while testing.
[dotest] Disable color while testing.

Disable colors so we don't risk having unexpected ANSI codes in the test
output. Currently, the behavior of a test can change depending on
whether it's run under a color-supporting terminal, or under a dummy
terminal, for example when using lit or multiprocessing.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@366356 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb