Add the capability on OS X to utilize 'xcrun' to locate the compilers used for building the inferior programs to be debugged while running the test suite.  By default, compilers is set to ['clang'] and can be overridden using the "-C compilerA^compilerB" option.
Add the capability on OS X to utilize 'xcrun' to locate the compilers used for building the inferior programs
to be debugged while running the test suite.  By default, compilers is set to ['clang'] and can be overridden
using the "-C compilerA^compilerB" option.


git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@152367 91177308-0d34-0410-b5e6-96231b3b80d8

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