Check that __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ is defined before comparing the value of it. <rdar://problem/26333564> 
Check that __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ is defined
before comparing the value of it.
<rdar://problem/26333564> 


git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@270015 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb