Swift expressions require OS X 10.10 / iOS 8 SDKs or later

Executable module set to "/home/rlovelett/Source/langserver-swift/.build/x86_64-unknown-linux/debug/langserver-swift".
Architecture set to: x86_64--linux.
(lldb) breakpoint set --file library_wrapper.swift --line 84
Breakpoint 1: where = langserver-swift`SourceKitter.Loader.load(path: Swift.String) -> SourceKitter.DynamicLinkLibrary + 1240 at library_wrapper.swift:84, address = 0x0000562d5aef5f78
(lldb) c
Process 5283 resuming
Process 5283 stopped and restarted: thread 1 received signal: SIGCHLD
Process 5283 stopped and restarted: thread 1 received signal: SIGCHLD
Process 5283 stopped and restarted: thread 1 received signal: SIGCHLD
Process 5283 stopped and restarted: thread 1 received signal: SIGCHLD
Process 5283 stopped
* thread #7, name = 'langserver-swif', stop reason = breakpoint 1.1
    frame #0: 0x0000562d5aef5f78 langserver-swift`Loader.load(path=<unavailable>, self=<unavailable>) at library_wrapper.swift:84
   81  	        // try all fullPaths that contains target file,
   82  	        // then try loading with simple path that depends resolving to DYLD
   83  	        for fullPath in fullPaths + [path] {
-> 84  	            if let handle = dlopen(fullPath, RTLD_LAZY) {
   85  	                return DynamicLinkLibrary(path: path, handle: handle)
   86  	            }
   87  	        }
Target 0: (langserver-swift) stopped.
(lldb) frame variable
path = <could not resolve type>
self = <could not resolve type>
fullPaths = <could not resolve type>
fullPath = <could not resolve type>
handle = <could not resolve type>
(lldb) po fullPath
error: expression failed to parse, unknown error
(lldb) po fullPath
error: Swift expressions require OS X 10.10 / iOS 8 SDKs or later.